Green’s Dictionary of Slang

latch n.²

(US black) a parasite, a beggar.

1968

‘Sl. of Watts’ in Current Sl. III:2.

In compounds

latch-lifter (n.)

(UK und.) ‘seed money’ for a planned crime.

1953

J. Phelan Underworld 58: Major Marsh, a notorious con-man, [...] once asked Bottom;ey toled him a hundred pounds for a latch-lifter.

In phrases

put the latch on (v.)

to beg from.

1951		Kerouac On the Road (The Orig. Scroll) (2007) 177: Diane is going to go and put the latch on a groom at the racetrack.
1957		Kerouac On The Road (1972) 73: Lee Ann is going to put the latch on a cashier at the racetrack.