We just learned about the big gated door called the Yett.
Another kind of castle fortification is a Hoarding.
This is a wooden shed that is built on the outside of a stone castle, to help protect archers and defenders of the castle during a battle.
These hoardings are usually not built on the castle until there is a battle.
When they are put up, there are holes in the side of a castle called putlogs or putlocks that they would put logs into, and then build the hoarding on top of that.
(from: wikipedia - hoarding (castle))
(from: wikipedia - putlog hole)
Kid Facts - Blast from the past: Spiš Castle