Features are disclosed for a stopping device that is resistant to forces in a first direction and compliant with forces in a second direction. The stopping device may be implemented in a roller top to restrict undesired horizontal movement of a payload being transported across the roller top. In some embodiments, the roller top can be implemented on a mobile robot to transport a payload between destinations. The stopping device can include a plurality of linkages to engage the stopping device and reduce forces applied to the stopping device by the payload. The stopping device, in an engaged position, may limit undesired horizontal movement of the payload. Further, the stopping device, in the engaged position, may respond to vertical forces applied to the stopping device by transitioning from the engaged position to a disengaged position.