The drum is free to rotate on the drive centre so wheel can go round but not the drum. It is the drive centre that is keyed to the axle
To use the drum the pins are pulled out of the wheel lobes so that just the axle and drive centre can rotate, the cable can free spool out when the pawl is not engaged, when it is engaged the drive centre’s teeth will then allow the drum to turn with the axle/ctr and wind in the cable.
Pawl goes towards the wheel so it engages with the teeth on the drive ctr