Definify.com

Webster 1913 Edition

Noun.

A string for raising the latch of a door by a person outside. It is fastened to the latch and passed through a hole above it in the door.

To find the latchstring out

to meet with hospitality; to be welcome. (Intrusion is prevented by drawing in the latchstring.)

[Colloq. U.S.]

latchstring ‎(plural latchstrings)

A string attached to a latch allowing it to be disengaged from the opposite side.