The crew is working to raise the anchor:
"Yo heave ho! Heave and pawl! Heave hearty ho!”
The capstan windlass has a ratchet that prevents anchor from going down between efforts. The pawl can ride up and over the slanting part of the teeth of the ratchet, and then drop down and engage on vertical part of a tooth.


pawl
n.
5akin ? to Du pal, pawl, stake, pole6 a mechanical device allowing rotation in only one direction: one type consists of a hinged tongue, the tip of which engages the notches of a ratchet wheel, preventing backward motion: see RATCHET, illus. Here's a diagram:
http://www.btinternet.com/~ajb.software/techweb/epscweb/mech1.htm