An attachment system for a boat cover using an insert strip press fit in a conventional rub rail channel fixed to the boat hull. The insert strip has a lengthwise slot which is configured to mate with a series of retainer elements attached about the perimeter of the cover. Each retainer element has a portion configured to be received in the insert strip slot and locked thereto by being turned sideways. In one embodiment, the retainers have a flattened pin which can be pushed into the insert strip slot and turned, a larger head portion thereby fit to a larger interior section of the slot to be locked therein. In another embodiment the retainer elements each have a pair of spread projections which are compressed together to be able to be pushed in through the slot entry section and which spring apart in the interior slot section, to be locked therein. A threaded pin can be advanced between the projections to produce a positive spreading of the projections. Racks and battens can also be attached to the insert strip using the same retainer elements.