I have seen the Cosom lifting devices, and have a couple. Mine are missing the pole. These were made to assist in placing a small boat on a car-top carrier.
How, exactly, were they used. Is there another piece other than transom clamp and pole? What would be the sequence to get the boat onto the car roof. I would probably have to involve foul language at some point to compliment the damage to the car and boat.
I have another oldie, no name. It mounts on a ball hitch. It has a big bolt on the mounting. Take ball out and mount on metal hitch. It has a transom mount on the top of the adjustable height. It swivels from the on ground position. Lift and walk around vehicle until in proper loading position. Fix swivel to no movement. Works well w/boat under 14" and under 200 #. I have owned/used since 1980. Bought from an old timer used.
The there’s the CDN made Tote-Um Pole. The boats transom is first secured to the pole which has been secured to the trailer hitch. Then the bow is lifted onto the vehicle. Only one person and one roof rack are needed to do it this way.