While the clip's design suggests that it can be used in a non-vertical position, this is not the case. My desk is too big for most clamps of this type, but it has a thin 1" shoulder that's perfect for using rotated 90 degrees where you can see the plastic housing is there to allow the lamp can slide stationary. This clamp cannot be tightened enough to be stable. Also, the plastic key on the clamp is not as strong and does not lock the nut in place as desired. Overall it's ok, but I would look elsewhere