Post #656294 by Atomic Tiki Punk on Sun, Oct 21, 2012 12:49 PM

Since this is a straight glass in a wood groove type of display case
many of the above suggestions may not apply, if the wood rail has become
warped or pitted,this can be a problem.

First you will need to clean the rails, you can use steel wool to clean and sand the inside
surface of the rails,you may need a tool (screw driver etc. with the steel wool)
to get deep into the rails depending on the depth.

Be careful not to damage the finish of the wood outside the area of the rails.

if this gives you more movement sliding the glass, then a bit of "Graphite Lubricant"
only in the groove of the rails (Top & bottom) will give the glass more movement
you can get it at most hardware stores and is fine for wood,does not stain etc.
you may have to apply it every couple of months.