Clamps for securing rollable devices such as utility poles to vehicles such as patient transportation vehicles are disclosed. In accordance with preferred embodiments, the clamp is comprised of mounting plate, leg guide, receiving pocket and variable cam for securing the utility pole to the patient transportation vehicle. The variable cam is preferably comprised of a section of an ellipsoidal solid surrounded by a bezel. The weight of a lever which rotates the variable cam is used to secure the variable cam and secure a utility pole within the pocket. The mounting plate of the clamp has multiple mounting locations such that the clamp can be used with numerous transportation vehicles and may be attached in various positions.