Confused - sail slides come loose from mast track

[Iliade]

I cannot quite get a feel for how high up the mast the gate is, but if the boom isn't running in the lower track, then maybe it was added because the lower track in the mast got damaged?

Did she originally have a roller furling boom that required the slides to be taken out of the track to furl or reef the sail?

 

[Akestor]

I was thinking about a plate or plates as in the picture blow that would close the sail entry slot and allow the sliders to fall below it without coming out of the track.
A pin like the one you show nearer the top of the track would solve the OP,s problem by supporting the goose neck higher up when stowing the sail

That's a nice installation for the OP and the high sitting pin on my mast. 2 moving plates with the black plastic stopper. Would it possibly work the other way around? permanent plates and removable stopper?

 

[duncan99210]

Originally the mast and boom was designed for roller furling of the main. The mainsail has a bolt rope, not sliders, so when you put a reef in the bolt rope slid out of the mast grove by way of the slot to wrap round the rotating boom. If you convert the set up to slab reefing and sliders for the luff, the you need to fit something along the lines of the photo Vic put up to stop the sliders coming out. A simple solutions is a pin set above the top of the feeder slot but that means you have to set the boom high enough to let the sail lie properly on the boom when reefed.
I have the roller furling set up on my Hurley 18: if anyone’s interested I can post picture on Monday.