Green’s Dictionary of Slang

block n.3

[block v.3 ]

1. an act of sexual intercourse.

[US] in G. Legman Limerick (1953) 54: There was a young man named Zerubbabub / Who belonged to the Block, Fuck & Bugger Club.
[Aus]B. Humphries Barry McKenzie [comic strip] in Complete Barry McKenzie (1988) 114: If it’s a flamin’ bloc [sic] she’s here for I reckon it’s only fair a bastard gives her one.

2. (N.Z. prison) a prostitute.

[NZ]D. Looser Boobslang [U. Canterbury D.Phil. thesis] 20/2: block 5 a dirty girl, generally one who is blocked [i.e subjected to group sex].

In phrases

on the block (adj.)

1. (N.Z.) subjected to group sex, thus vtr put (someone) on/over the block.

[NZ]A. Duff Once Were Warriors 193: [G]iving Nig Heke this terrible look as if he was ta blame for putting herself on the block for all the fullas to fucker.
[NZ]D. Looser Boobslang [U. Canterbury D.Phil. thesis] 20/2: on the block 1 (alsoover the block) subjected to group sex, rape and/or sodomy (often gang associated) [...] put on the block 1 (also put over the block) to subject (a person) to group sex, rape or sodomy.

2. (N.Z.) ostracised, ‘sent to Coventry’.

[NZ]D. Looser Boobslang [U. Canterbury D.Phil. thesis] 20/2: put on the block 2 to ostracise and ignore a fellow inmate.

3. (N.Z.) assaulted, beaten up by a group.

[NZ]D. Looser Boobslang [U. Canterbury D.Phil. thesis] 20/2: put on the block3 to subject (a person) to a physical assault. This may take the more organised form of a pack attack (group assault) .