Heavy Mech Support Platform (SDKS-EN008) [Structure Deck: Seto Kaiba]

Once per turn, you can either: Target 1 Machine-Type monster you control, equip this card to that target, OR: Unequip this card and Special Summon it in Attack Position. While equipped by this effect, the equipped monster gains 500 ATK and DEF. (A monster can only be equipped with 1 Union monster at a time. If the equipped monster would be destroyed, destroy this card instead.)