I am really pleased with the way bolts fit into the spaces for them:
If you don't work with clay, you are probably wandering why is this such a big deal. The thing is, the clay shrinks...and every clay shrinks differently so the exact size is difficult to predict if you have not tested the clay.
Here is the shrinkage example:
First triangle (top left) is freshly made, second is leather hard and third bone dry.
Bottom row: first is bone dry, second bisque fired and third glaze fired to 1210oC.
Lines are 3 cm apart.