Steam Engine notes part number 12 is a compression spring. THis spring mounts around the spring shaft and holds the cylinder (part #2) against the base (part #1). It is important to place a flat washer between the spring and the plexiglass, failure to do so will cause the spring to dig into the plexiglass. part #13 is the base.....have some fun and design your own! Remember that it must be stable enough to balance the running engine and have clearance holes to match up with the 1/4-20 screw holes in part #1. the heads of these screws must be buried in the metal so the base will sit flat. Assembly first mount part #1 to your base parts 3, 7, and 9 must be assembled next assemble parts 4 and 5 slide part 9 into part 5, then slide part 3 into part 2. slide part 11 into part 4, then screw it into part 2. add a flat washer, and part #12 then tighten part #10 onto part #11. install part #8 onto part #9 and tighten with a set screw. screw part #6 onto part #1 and we are done! (sounds easy doesn't it) good luck,