The relationship between sailing and rigging is very clear, and rooted in history. However, I think that it is sometimes forgotten that sailing and boat rigging have undergone advances in technology that is still very useful in theatre.
The series of links below illustrate a variety of sheaves that can be mounted from a stanchion (or in our case, pipe). While a piece could certainly be made by most shops that would do essentially the same thing, I thought the choices where interesting, and at good prices. I know that there have been pieces I have rigged in the past where being able to directly connect the sheave to the pipe, instead of making a bracket would have been convenient.