My brother Bob had the answer in about 5 minutes!
The weights are hung on the bottom of my fenders to keep them from squeezing up and out of the gap between the boat and the concrete pier that we are tied to.
Hope they work!!
PS> In New Zealand, they just fill coffee cans with concrete and stick and eye bolt in the top as it cures. Then they hang the coffee cans from fenders. We didn’t have time to go through the construction process here.