A portable clamp has a hinged, two piece arm that folds for storage within a hollow stem. A first arm hingedly connects to a second arm where each has a curved shell sized for gripping the frame of a bicycle. The first arm and second arm have cooperating holes to admit pins for securing the first arm to the second arm. Opposite the hinge, the second arm fits perpendicularly into the stem. A buckle secures a strap that passes around an object. In use, a cyclist releases the clamp from the stem. The cyclist places the strap around the upright object at a desirable height. The cyclist places the end of the strap in the buckle and cinches the strap. Using a pin, the cyclist secures the clamp within the stem. The cyclist places the arm around a bicycle frame member then secures a pin through the arm and into the stem. The bike is then supported at a convenient height.