Keilim 24:1

There are three kinds of shield: a bent shield is susceptible to midras impurity, a shield used in the arena is susceptible to corpse impurity and the toy shield of Arabs is insusceptible to all types of impurity.

Keilim 24:2

There are three kinds of wagon: one designed like a carriage is susceptible to midras impurity, one designed like a bed is susceptible to corpse impurity and one used for stones is insusceptible to all types of impurity.