In olden times it was a staff about 3 feet long, having a sharp point at the foot to stick in the deck, and a forked head to hold a lighted match. It gave way to the less dangerous match-tub, and since that to gun-locks, friction-tubes, &c. Shakspeare in Henry V. says:
"And the nimble gunner
With linstock now the devilish cannon touches,
And down goes all before them."