Green’s Dictionary of Slang

(UK Und.) the highest level of pick-pocketing; thus queer a stilt v., to steal a pocketbook.

1822		Life and Trial of James Mackcoull 5: Mackcoull returned [...] without attempting to queer a stilt * To steal a pocketbook.
1866		J. Greenwood Little Ragamuffin 295: You are a nice sort of chap to try your hand at stilting (first-class pick-pocketing!).