Green’s Dictionary of Slang

block n.6

[SE block, an impediment]

In phrases

put a/the block on (v.) (also put the blockers on, put the blocks to, put the box on)

[1910s+] to interfere with, to stop someone’s actions or plans, to defeat, to overcome.

put the blocks on (v.) (also put the block(s) to)

1. [late 19C+] to give someone a hard time.

2. [1940s–50s] (UK prison) to tighten up regulations that have become temporarily lax.