18", 24" and 28" Backirons are designed to hold up your TruForm armature or regular armature and the 16" Backiron for your regular armature. The nuts on the vertical all thread allow you to adjust the height of your sculpture. The ends of the horizontal all thread on the 28" Backiron will hold 1/4" wire. The 18" and 24" Backirons have grooves for securing 3/16" armature wires to. Just secure to your wood base and create a masterpiece!