Portcullis

A portcullis is a gate-like device used in castles to seal entrances when a castle was under siege. They were typically made with wood or metal and had sharp, spiked bottoms to injure or kill intruders when it was closed on them.

The Doctor was almost killed by one when attempting to escape Stockbridge castle in the midst of escaping the Rutan-controlled Turkish Knights. (AUDIO: Castle of Fear)