The top of the femur bone in dogs is known as what? the rod the lensil the bell the caput

The answer based on the given description above is the term CAPUT. The caput is the area of the bone among dogs that is rounded. Typically, this is found at the top of the femur bone in dogs or at the end of the femur and fits into the acetabulum. Hope this helps.

Active site is where they touch.

This movement is also referred to as  glacial plucking