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Guide · Layout · Chalk reels, marking chalk and lumber crayons

How do you use a chalk line, and which chalk comes off? Chalk reels and refills, blue vs red vs white vs black chalk, permanent and temporary chalk, snapping a line on a roof, wall or slab, the 3-4-5 rule, lumber crayons and keel, and chalk removal

A chalk line is a reel of string in a box of powdered chalk: hook the end, pull the line tight across the surface, lift the middle a few inches and let go, and the string snaps a straight chalk mark the whole length. Blue chalk is the everyday layout chalk and brushes or washes off; white is the lightest and cleanest; red is semi-permanent and used where the line must survive weather and traffic; black and fluorescent orange are permanent and stain. Roofers snap red or blue lines on felt and underlayment to keep shingle courses straight and black or orange on a deck that will be covered. A lumber crayon (keel) is a wax crayon for marking lumber, concrete and metal that rain does not wash off; most lumber crayon marks on concrete fade but do not fully wash off.

Bayshore Safety. Industrial safety, roofing tools and jobsite supplies since 2017. · Current as of November 2026 · the C&R chalk and reel product data on this site (CH-25 100 ft all-metal red chalk box; TR-150 100 ft speed reel with ABS case and polyester line; HCR-15G 115 ft rubber-grip reel; Little Giant G110 110 ft and G150 150 ft reels that hold about a pound of chalk; 8 oz marking chalk in blue, lime, red, glo-orange, yellow, white and black; 5 lb marking chalk in blue, red, white, black and glo-orange; lumber crayons in blue, red, yellow and white); the chalk permanence convention the chalk manufacturers print on the bottles (blue and white temporary, red semi-permanent, black and fluorescent permanent)
Chalk reels, chalk and crayons we stockAll roofing tools
C&R CH-25 Chalk Line Reel, 100 ft, All Metal, RedC&R CH-25 Chalk Line Reel, 100 ft, All Metal, RedThe product data lists the Little Giant G110 as a 110 ft reel that holds almost a pound of chalk
$76.80See the product

A chalk line is three choices. The reel (a small speed-reel box with a 100 ft line for layout, or a big-capacity reel like the Little Giant that holds a pound of chalk for all-day roofing), the chalk color (which is a permanence choice as much as a visibility one) and the line itself (a braided cotton or polyester string that holds chalk; the thinner the line, the finer the mark). The questions below are the ones layout crews ask: how to use one on a wall and on concrete, which chalk is not permanent, which color shows on concrete and on black felt, how to pop a straight line alone, what the 3-4-5 rule is, what a lumber crayon is for and whether it washes off, and how to get chalk out of clothes. The films and apparel brands that share the name are not covered here.

Chalk lines and chalk, question by question

Reel capacities and chalk colors are from the product data on this site; the permanence of each color is as the chalk manufacturers label it.

How do you use a chalk line reel, and how do you pop a line on a wall?Fill the box with chalk (a 100 ft reel takes about 2 to 4 oz, the Little Giant about a pound), close it, and shake so the line coats as it feeds. Hook the end tab on a nail, a shingle edge or a helper’s finger at one mark, walk the line out to the second mark, pull it tight and press it to the surface with a thumb, then lift the line straight up a few inches near the middle and release so it snaps down in one plane; lifting it sideways curves the mark. On a wall, hook the tab at the top mark and hold the bottom, or set a nail; on a long run, snap in two halves from a center point. Rewind with the crank; a speed reel rewinds several times faster than a plain one, which is why layout crews buy them.
How do you use a chalk line on a roof, and how do you snap a line alone?Roofers snap horizontal lines across the underlayment every few courses (every course on three-tab, every two to three on architectural shingles, at the exposure the shingle manufacturer gives) and vertical lines at the rake offsets so the shingle joints stagger correctly; the line is measured up from the eave at both rakes so the courses stay parallel to the eave, not to the ridge. Alone: hook the tab on a roofing nail driven half way at one mark (the tab has a slot for it), or on the edge of a shingle, and snap from the other end. On felt and synthetic underlayment blue or red chalk shows; on black felt white or fluorescent shows better.
Which chalk is not permanent, and what do the colors mean?Chalk makers label permanence on the bottle, and the convention holds across brands: white and blue are temporary (they brush, blow or rain off, and are the chalks for anything that will be seen afterward: drywall, concrete that stays exposed, finished wood); red is semi-permanent (survives weather and foot traffic for days to weeks and stains porous surfaces); black and fluorescent orange, pink and lime are permanent (they are dyes as much as chalk and are for roof decks, framing and outdoor layout that will be covered). Yellow sits between blue and red. Glo-orange is for visibility in low light and on dark material and is permanent.
What chalk color shows on concrete, and what chalk for a chalkboard?On gray concrete, red, black and fluorescent orange show clearly; blue is visible and temporary; white vanishes. Use blue where the slab will be exposed and the line should disappear, red where the line must last through the pour prep or the framing. Chalkboard chalk is a different product (calcium carbonate or gypsum sticks) and does not go in a reel; marking chalk is a fine powder with pigment and sometimes a dye.
How do you get chalk off concrete and fabric?Blue and white: sweep, blow or hose. Red: scrub with water and a stiff brush; it fades but can leave a stain on porous concrete. Black and fluorescent: they are permanent on concrete and are removed only by grinding or covering. On fabric, chalk comes out in a normal wash; red may need a pre-treatment; black and fluorescent dyes can set permanently, which is why roofers keep a set of work pants for layout. On a finished floor or carpet, vacuum first and never wet-scrub a dye chalk, which drives it in.
What is the 3-4-5 rule in carpentry, tiling and for squares?A triangle with sides 3, 4 and 5 (or any multiple: 6-8-10, 9-12-15, 30-40-50) has a right angle between the 3 and 4 sides, so it checks or lays out a square corner on any scale: measure 3 feet along one line from the corner, 4 feet along the other, and the diagonal between those marks is 5 feet if the corner is square. Tile setters use it to square the first row to the room, framers to square a deck or a foundation, roofers to set a rake line square to the eave before snapping the vertical chalk lines. A framing square does the same thing at short range; the 3-4-5 does it across a whole slab with a tape and a chalk line.
What is a chalk line reel called, and what line length do I need?Chalk line, chalk box, chalk reel, snap line, chalk line reel; the small plastic ones are speed reels, the big metal ones are contractor or giant reels. 100 ft is the standard and covers any residential roof; 110 to 150 ft reels (our Little Giant G110 and G150) carry a heavier line and far more chalk for crews that snap lines all day on commercial decks. The line is replaced when it frays; braided polyester or cotton line is sold by the 100 ft hank and threaded through the box.
What is a lumber crayon, what is keel, and does it wash off concrete?A lumber crayon is a hard wax crayon, square or hexagonal so it does not roll, for marking framing lumber, plywood, concrete, block, steel and pipe; keel is the trade’s old name for it (from the red ochre crayons the lumber graders used). It marks wet wood and rough surfaces where a pencil skips and does not wash off in rain. On concrete the mark fades with sun and traffic over months but does not wash off with water; a solvent (mineral spirits) and a scrub removes it from a slab, and it comes off steel with a solvent wipe. Our crayons come in blue, red, yellow and white by the dozen; red and yellow show on wet lumber and gray concrete, white on dark membrane and black felt.
What is the story behind the chalk line?The snap line is one of the oldest layout tools: Egyptian and Roman builders snapped lines with a cord rubbed in ochre or charcoal, Japanese carpenters use an ink line (sumitsubo) with silk thread, and the chalk-filled reel with a crank is a nineteenth-century American pattern that has not changed much since. The films and clothing brands with the same name are unrelated and not covered here.

Chalk lines in plain words

  • Hook the tab, pull the line tight, press it down, lift straight up in the middle, let go.
  • Blue and white wash off; red is semi-permanent; black and fluorescent orange are permanent dyes.
  • Roof layout: lines measured up from the eave at both rakes, every one to three courses, at the manufacturer’s exposure.
  • On concrete red and black show and stay; blue shows and leaves; white vanishes.
  • 3-4-5: three along one line, four along the other, five on the diagonal means square. Works at any scale.
  • Speed reels rewind fast; giant reels hold a pound of chalk for all-day roofing.
  • Lumber crayon (keel) marks wet wood, concrete and steel and does not rain off; solvent removes it.
  • Dye chalk on clothes is permanent; keep layout pants.

Questions people ask

How to use a chalk line on a wall?

Hook the tab at the top mark (on a nail if alone), hold the line tight at the bottom mark, press it to the wall, lift the middle straight out and release.

What chalk line is not permanent?

Blue and white chalk; red is semi-permanent and black and fluorescent colors are permanent.

What is the 3/4/5 rule for tiling?

Measure 3 units along one line and 4 along the other from the corner; a 5-unit diagonal means the corner is square, so the first row is laid square to the room.

What is the 3/4/5 rule in carpentry?

The same right-triangle check for squaring a deck, a foundation or a wall, at any multiple of 3-4-5.

What chalk color is for concrete?

Red or black for a line that must last; blue for one that should disappear; white does not show.

What is the story behind the chalk line?

A snapped cord rubbed in ochre is thousands of years old; the chalk-filled crank reel is a nineteenth-century pattern still in use.

Do lumber crayons wash off concrete?

No; the wax mark fades with sun and traffic but needs a solvent and a scrub to remove.

How did the chalk line end?

If you mean a film or series of that name, it is not covered here; this page is about the layout tool.

How do you use a chalk line reel?

Fill it with chalk, shake, hook the tab, pull tight, snap from the middle, crank to rewind.

How do you pop a chalk line?

Press the tight line to the surface with a thumb, lift it straight up a few inches and let it snap down in one plane.

What is the chalk line for?

Snapping straight layout lines on roofs, walls, floors and slabs that are longer than any straightedge.

How do you remove chalk lines from fabric?

Normal washing for blue and white, a pre-treatment for red; black and fluorescent dye chalk may not come out.

What is the 3/4/5 rule for squares?

A check that a square or a corner is true: 3 and 4 along the legs, 5 on the diagonal.

When was the chalk line invented?

Snap lines are ancient; the crank reel filled with chalk dates to the 1800s.

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