Heavy Mech Support Platform (SBCB-EN066) [Speed Duel: Battle City Box]

Once per turn, you can either: Target 1 Machine monster you control; equip this card to that target, OR: Unequip this card and Special Summon it. A monster equipped with this card gains 500 ATK/DEF, also if the equipped monster would be destroyed by battle or card effect, destroy this card instead.