Meaning of chalk line

chalk' line"

Pronunciation: [key]
— Building Trades. Building Trades.
  1. a chalked string for making a straight line on a large surface, as a wall, by holding the string taut against the surface and snapping it to transfer the chalk.
  2. the line so made.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.