The billy club was a weapon used by Daredevil.
When Matt became Daredevil he created what he called his Billy Club.
Daredevil's Billy Club could be the size of a nightstick or extend to the size of a pole vault.
The Billy Club had a built in grapple hook which Daredevil could use to swing from building to building.
The Billy Club could also detach in the middle while connected to a rope. In this form Daredevil could use the Billy Club as a nunchaku-like weapon.
In the comics
The first version of Daredevil's billy club in the comics was a nightstick that Matt Murdock stole from a police officer when he was a child.
Murdock later upgraded his billy club to include a grapple hook and a rope in the middle that when pulled apart became a nunchaku-like weapon.
An early version of the billy club had a police scanner built into it.