These assembly puzzles require the puzzler to combine and arrange several pieces to create one, unified object. Once solved, they can be used as desk ornaments, sculptures, stress relievers or just put out on display. Difficulty: 4/4 Part of our True Genius brainteaser collection -- a best selling brand for stores selling smart, bookish gifts. Perfect for Father's Day, this makes a thoughtful gift for dads who enjoy a mental challenge, problem-solving, and hands-on puzzles.