Although these upgrades work in different ways their effects are the same. They allow an Ork vehicle to attack an enemy vehicle in close combat. The Ork vehicle must move into contact with the target vehicle during its movement phase but may not attack if it moved more than 12".
The Ork vehicle may shoot in the shooting phase as normal and then resolves an attack in the assault phase. The vehicle has one attack for each upgrade listed (ie, a vehicle with a boarding plank, big grabber and ram would have 3 attacks). Attacks hit on a 4+ regardless of the target's speed and are resolved with a Strength of 6. Walkers, skimmers, infantry and any other models that have a WS characteristic may not be attacked as these weapons are too cumbersome to be used against them.