US Patent 7770300 Chalk line

The chalk line comprises a housing that supports the spool having a string or line wound thereon in a chalk chamber. The transmission for rewinding the spool is located in a separate compartment. The chalk filled chamber is isolated from the transmission such that the components located in the chamber are the spool, line and chalk. A door for allowing access to the chamber is opened by manually operating a latch. A safety interlock is also provided such that the latch cannot be inadvertently unlocked.