Wow, I didn't expect this to be possible in Mechanica (or whatever its called these days).
Just a thought: since the contacts in Mechanica are frictionless (I trust Mats' statement), then making a model where the glass plate has forced displacement in y-direction with value of half glass thickness would give the same results as the more complicated sliding of the glass. (This may be done in Mats' plane strain model already, I didn't open it).