[C320-list] Extra mast track?

[Robert Seastream]

All:

I was taking the sails off my 2002 (in mast furling) and noticed a 
track in the mast to the left of the sail entry point for the mainsail 
furling system.
The track looks large enough to accommodate the bolt/bead that's sewn 
into the luff of a sail, but not large enough for sail slugs or other 
cars.
I can't see raising and lowering a sail in it, since that would mean 
taking the sail completely off after each use.
Anyone have this in their mast and know what it's for?

Bob Seastream
'Intuition' # 906