A mounting device or clamp is provided that can be secured to a roof joint without damaging the roof joint. Two roof panels can be joined at a roof joint that extends away from the roof. The clamp has a body with a slot to receive the roof joint. An insert of the clamp is rotatable relative to the body from a first position to a second position. The clamp body can be positioned over the roof joint, and the insert can rotate or pivot from the first position to the second position relative to the body to secure the clamp to the roof joint. In one embodiment, a body of the clamp has a first arm that is concave and the insert has a concave portion to engage the roof joint. Alternatively, in another embodiment, the insert can be connected to the clamp body such that either a first projection or a second projection of the insert faces a roof joint.