Creating the thin silicon gasket:
1.Place the two opposing glass doors into the tracks.
2.Mark the overlap between the two panes of glass
3.Use surgical spirits to degrease and clean the two edges that overlap
4.Place a wide length of masking tape on the front face of the back sheet
5.Use a straight edge and a sharp scalpel bale, cut an approximate 5-8mm gap in the masking tape, 5mm from the edge.
6.Use a small amount of Surgical spirits to clean this small exposed strip of glass.
7.Place several wide length of masking tape on the back side of the front sheet of glass.
8.Lightly coat the masking tape on the front glass with a thin layer of petroleum jelly.
9.Place the back sheet of glass back into the track.
10.Use a pencil and mark the masking tape just above the bottom track.
11.Push the glass as high as is needed to be able to lift it out of the bottom track.
12.Use a pencil and mark the masking tape just below the top track.
13.These marks will indicate the end points of the gasket.
14.Run a small bead of clear silicon sealer over the 5-8mm gap in the masking tape, between these two marks.
15.Carefully place the front sheet of glass back in the track.
16.You should now have the wet (uncured) silicon sandwiched between the two sheets of glass.
17.Leave to cure for at least 24 hours.
18.Carefully remove the font sheet of glass from the track.
19.The layer of petroleum jelly should prevent the silicon from sticking to the masking tape.
20.Remove the back sheet of glass and lay it on a flat surface.
21.Use a new, sharp scalpel blade and a straight edge, cut through the cured silicon to the line of the masking tape.
22.Make the above cuts at a slight angle.
23.Remove all masking tape with excess silicon and degrease the sheet of glass and the new silicon gasket.
24.Place both sheets of glass back into the tracks.
The multiple layers of masking tape should have allowed a small gap between the gasket and the front sheet of glass.
This allows the two sheets of glass to be able to slide past each other with out binding up.
I hope the above explanation helps, if there are any question, feel free to ask.