 Sometimes the connection is tight enough to pick up a solved part by holding one piece.Some fully interlocking puzzles have pieces all of a similar shape, with rounded tabs out on opposite ends, with corresponding blanks cut into the intervening sides to receive the tabs of adjacent pieces.Other fully interlocking puzzles may have tabs and blanks variously arranged on each piece, but they usually have four sides, and the numbers of tabs and blanks thus add up to four.