I am trying to set up a simulation representing a large payload being strapped to the deck of an aircraft. The payload has tie downs with cylindrical holes along both sides which allows a shackle to be attached and then tied to the ground. How would I represent that within simulation as far as Fixtures are concerned without over restraining the model? I considered doing a split line to represent where the shackle will sit when tension is applied, but not sure about the directions to restrain it in.