They were fully trained, strong, professional warriors Definition.  Armed with a shield and a battle-axe.  They could join together and use their shields to form a shield wall.

The shield wall did not just stand still.  For the Housecarls to use their battle-axe, they would have to move apart slightly.  This gave them space to swing the axe at the enemy.  Parts of the shield wall would move forward together to attack.

Saxon Shield Wall
 
Saxon Housecarl The Housecarls were probably the best warriors Definition in Europe.  Unlike William's forces, the Housecarls were loyal to Harold whatever happened - money didn't matter to them!