Anti-theft structure for travel trailers including fore and aft spurs depending from the fore and aft ends of the trailer. In normal use, the spurs do not support the trailer but rather thrustingly engage the ground, or other surface upon which the trailer is resting, when an attempt is made to move the trailer. The respective spurs are slidably received in vertically disposed tubular housing members which define openings through the floor of the trailer. Accordingly, the upper ends of the spurs are accessible only from the interior of the trailer. Thus, when the door to the trailer is locked, access to the upper ends of the spurs is denied. The upper ends of the spurs are securely held in selected ones of several extended vertical positions by holding structure which may be actuated only from the interior of the trailer. Additionally, the respective holding structure may be secured to the housing members by suitable padlocks or the like to provide further assurance against unwarranted removal of the spurs.