© 1998-2015 by Marvin Hull
The castle's entrance was its weakest point, so priority was given to building a strong gatehouse. Often this part of the castle was the first to be rebuilt in stone. The conversion of the gatehouse into stone protected it from attack by fire, but also from other kinds of assault.

Placing the gatehouse near a moat, keep, or other tower gave it added protection. Frequently, the protecting tower was built into the gatehouse, as at Pembroke, which is defended by adjoining towers.

Gate-towers appeared in the late 12th century. The first gatehouses were small square towers, with doorways at the middle of the bottom storey. They usually housed the castle constable. In the 13th century, architects added a pair of wall towers to flank and protect the gate. Eventually, the two towers merged into one large tower, which housed the guards or members of the lord's household. It also provided space for a prison, guardrooms, or larger living areas. Sometimes the gatehouse even served as a keep.

Most gatehouses rose three storeys high. The ground floor contained the guard rooms. The first floor held residential quarters and contained the machinery to operate the portcullis. The second floor was used by the garrison and to store weapons. Often gate passages had murder holes and arrow slits. A barbican frequently defended the entire gatehouse.

Gatehouses maintained their importance for centuries, even in later castles which were not much more than semi-fortified manor houses. Many have survived where all other traces of the castle have vanished.