A machinist jack is a simple but extremely useful tool used in machine shops for leveling and supporting parts in a vice. It is particularly useful for long parts and parts on angles.
Consider this an affordable albeit light duty alternative to a steel set: (Steel version linked on amazon here: http://amzn.to/28MtWex)
I printed everything at 50% hexagonal infill. I recommend using a light support that you can easily remove after printing such as a 6mm pattern spacing, 6mm interface pattern spacing, and 1 interference layer
The blocks are designed for a 1.25" long fully threaded 5/16" bolt. (I used a nylock nut and threaded rod in the photo because I didn't have a fully threaded bolt available.)