The winch that hauls the boat onto the trailer from the water should have a roller in it to keep the strap or rope from fraying from rubbing against stuff. This model is a self-centering roller for either a flat strap or a rope. Self centering is accomplished by the slight taper from the outside edges to the center length of the roller.
The roller will make it easier to winch in your boat. Print in PETG and put some grease in the hole as you fit a shoulder-bolt into the 10mm hole. A 7/16 shoulder bolt should fit perfectly :)
I printed mine with 20 perimeters to make sure there was no weak infill to get crushed - solid circular distribution of the load.
Happy boating!
The author hasn't provided the model origin yet.