"Twelve" was just plain sloppy. It's 12 inches in a foot so inches should be the clue to be consistent. Contract and Will are both legal documents that are usually said to be "drawn up". Okay, but "laugh" and "blank" would be better for variety.

Thanks for the suggestions! I'll make some adjustments. I'm still getting used to this style, some of my other, non-puzzgrid, work is better.

The "smith" category is ill conceived. Half of them are proper whole names, while the other half are professions. Willow Smith, Sam Smith, coppersmith, and locksmith -- how do those complete the category "___ Smith"? Answer: they don't. They complete two different categories, one "___ Smith" and the other "___smith."

The other categories are at least fair, though "replace any one letter for an element" is, in my opinion, pretty weak. It's a bit too abstruse. A solid word connection is consistent, e.g. "replace the *first* letter for an element."

12 ribs per side, 24 in total. They join at the sternum and each eminates from the side of a vertebra, 12 left and 12 right.