In its simplest form, an arrowslit was a narrow vertical opening; however, the different weapons used by defenders sometimes dictated the form of arrowslits. For example, openings for longbowmen were usually tall and high to allow the user to shoot standing up and make use of the 6 ft (1.8 m) bow, while those for crossbowmen were usually lower down as it was easier for the user to shoot whilst kneeling to support the weight of the weapon.