The chalk reel was a box with a string inside it. The string was coated in chalk dust. You pulled the string out of the box and stretched it between two points and snapped it and the string hit the surface and left a straight chalk line. The chalk reel drew a straight line faster than any ruler. The ruler drew a line three feet long. The chalk reel drew a line thirty feet long. The chalk reel was the ruler that outgrew the classroom.

The snap was the moment. You held the string at one end. Your partner held the other end. You pulled the string tight against the surface. Then one of you pinched the string between thumb and finger and pulled it away from the surface one inch and let go. The string snapped back. The snap deposited the chalk in a line. The line was straight because the string was straight and the string was straight because the tension was even. Two people pulling equally from opposite ends. The chalk line was a collaboration. You could not snap a chalk line alone.

The chalk was blue or red or white depending on the surface. Blue for plywood. Red for concrete. White for steel. The color made the line visible against the background. A blue line on blue steel would disappear. A white line on white drywall would disappear. The carpenter chose the chalk the way a painter chooses a color. The color was functional. The color was information. Blue chalk said this line was snapped by a framer. Red chalk said this line was snapped by a concrete worker. The line identified the trade.

The chalk line was temporary. The chalk washed off in the rain. The chalk smudged when you touched it. The chalk blew away in the wind. The chalk line was the most temporary mark on the job site and the most important mark on the job site. Every wall started with a chalk line on the slab. Every roof started with a chalk line on the sheathing. The most permanent structures in the building began with the most temporary mark. The chalk line said build here. Then the chalk line disappeared under the building it created.

They use laser lines now. The laser projects a line on the surface in red or green light and the line stays as long as the laser is on. The laser line does not smudge. The laser line does not blow away. The laser line does not need a partner to hold the other end. The laser line is a solo act. The chalk line was a duet. You needed somebody at the other end of the string. The person at the other end was your partner and the partnership produced the line and the line produced the wall. The laser eliminated the partner. The laser is more efficient. The chalk line was more human. The wall does not know the difference. The carpenter does.

See also: Mason Line, Plumb Bob