Green’s Dictionary of Slang

wedge n.2

1. the penis [it wedges open the vagina].

[UK] ‘Young Collin’ in Farmer Merry Songs and Ballads (1897) IV 260: Young Collin [...] told his Wife who the Cause would know, / That Hem made the Wedge much further go.
[UK]Cleland Memoirs of a Woman of Pleasure (1985) 154: He [...] nailed this tender creature with his home-driven wedge.
[UK]‘The Lady’s Water-Spout’ in Randy Songster in Spedding & Watt (eds) I 209: But, says he, I can see, that before I begin, / To stop up the hole I a wedge must thrust in / [...] / Then down on his knees hard at it went he, / He thrust in his wedge as tight as could be, / Drive away, said the lady, go it pell mell.
[UK] ‘The Water-Spout’ in Rakish Rhymer (1917) 72: He drove his wedge into the top, / But soon found it did fit ill.
[UK]Farmer & Henley Sl. and Its Analogues.
[US] in G. Legman Limerick (1953) 248: A horny young fellow named Redge / Was jerking off under a hedge. / The gardener drew near / With a huge pruning shear, / And trimmed off the edge of his wedge.

2. (US campus) in fig. use, a derog. term for a hard worker.

[US]Baker et al. CUSS 219: Wedge A person who studies a great deal.