WordNet sense 1 (small markers inserted into a surface to mark scores or define locations etc.):

pin

WordNet sense 2 (informal terms of the leg):

stick

WordNet sense 3 (a prosthesis that replaces a missing leg):

leg, pegleg, wooden leg

WordNet sense 4 (a holder attached to the gunwale of a boat that holds the oar in place and acts as a fulcrum for rowing):

oarlock, thole, tholepin, rowlock

WordNet sense 5 (a wooden pin pushed or driven into a surface):

nog

WordNet sense 6 (succeed in obtaining a position):

nail, nail down

WordNet sense 7 (fasten or secure with a wooden pin):

peg down