As an alternative to the time-consuming task of creating a breach, an escalade could be attempted to capture the walls with fighting along the walkways behind the battlements. In this instance, attackers would be vulnerable to arrowfire. A safer option for those assaulting a castle was to use a siege tower, sometimes called a belfry. Once ditches around a castle were partially filled in, these wooden, movable towers could be pushed against the curtain wall. As well as offering some protection for those inside, a siege tower could overlook the interior of a castle, giving bowmen an advantageous position from which to unleash missiles.