The mast track normally has an entry point with a 'gate' but this is above deck for the sails etc. Anything put on without a gate is likely using a simple bolt small enough to slide in at an angle and then big enough to clamp down when in normal operation. Alternatively you can simply grind it flat on either side and then insert and twist. A cam can be used to tension.
look up t slot nuts and cams
No Im in Essex, Not dried out in Poole Harbour Im afraid.Tranona
I recently read a post you made referring to a few places where it is possible to dry out I Poole harbour. Could you please tell me where these spots are as I'm trying to do just that with my 1.6 m draft .com keep this weekend.
Many thanks