A clamp includes first and second parts, each of the parts having a circular central section and a pair of straight extensions extending away from the circular central section in opposite directions. In the first part the holes are closed holes, while in the second part the holes are open holes, connected by slots to an upper edge of the part. Bolts may be pre-located through the closed holes, with nuts threaded onto the bolts, but not tightened. The pre-placed bolts may be received through the slots and into the open holes of the second part. The nuts may then be tightened against the second part to clamp the circular central sections on opposite sides of a circular object, such as a vertical pipe run, between the parts. According to a variant, the bolts are permanently secured to the first part so as to prevent rotation of the bolts.