Castles usually had two portcullises, one closer to the inside and another farther away.
The presence of these two gates was useful for trapping enemies and attacking them from the castle’s barbican. For example, soldiers could drop hot oil from holes in the ceiling, while archers and crossbowmen could shoot missiles from arrowslits on the sides.
The portcullis had to always be in a state of readiness. The winching mechanism that allowed the portcullis to be raised also helped it get released very quickly by letting go of the ropes and chains.
Castles could have more than one portcullis, depending on their size and when they were built. Castles that were built concentrically had many and could use them strategically to stop and deal with enemies. For example, attackers could be lured inside the gatehouse passageway. Once they were inside, one or more portcullis could be dropped at the same time, trapping them. Defenders could then throw heavy objects, hot liquids and arrows from the gatehouse and the barbican.