WHEEL BATS - Industrially made
ca: DISCOS - Fets Industrialment
es: DISCOS - Hechos industrialmente
The illustration on the left show how wheel bats are used together and on the right the small protruding polls attached to the bat which slips into the holes of a bat that is put on top to hold it place. 
a) Bat with a jar and holes for bat pins. b) Bat with bat pins and holes for screws. c) Wheel head with holes for screws, d) Small poll, e) Screw