I use this type of locking system -- http://www.marinelock.com/Kayak-Lock-fits-9-to-13-_p_43.html It is basically a cable and brass lock. I loop it through both of my Merc trolling motor clamps, then looped through one of my Cannon Mini Mag downrigger, then looped through how ever many reels are in the rod holders and the rod holders themselves, and finally looped through the other Cannon Mini Mag downrigger. It's a bit of a Pain in the Azz to secure or unlock, but it seems to have worked out OK at the PA Boat Harbor moorage for a couple of years. I know it is ot foolproof, nothing really is, the strategy is to make it more difficult to steal mine than other boats. And if you get multiple locks, you can have them all keyed the same.