Or maybe tractor beam (like in Star Trek).. could be used by large ships to lock on and slowly pull a ship towards them and smaller ships vs. large could reverse the beam to pull themselves towards the hull. Once contact to hull is made a hatch could open, exposing access to the hull where you can attempt to breach through. For defense against this, there are evasive maneuvers you could initiate in order to escape the beam or with enough engine power just thrust right out of its grip.