I don't have any good pictures of that part of my cab - I'll have to take some. I'll try to put into words what I did:
- I went with clear glass (some like smoked glass), 1/4 inch thick. A 30"x24" sheet was about $30
- On the left and right side of my cabinet, the montior opening space, I put two stips of 1x1 wood (painted black). The wood is recessed from the front edge of the cab by a touch more than 1/4". The glass "rests" on these strips of wood, so that the glass is almost flush with the side of the cab. If you want the glass recessed a bit, just install the wood strips a bit deeper into the cab.
- On the bottom, I have wood that the glass rests on as well. You could do a similar recessed wood strip thing. I got a U shapped clear plastic channel thing from Home Depor (it is reaklly a rope light holder), I put that on top of the wood on the bottom and the glass slides down into it (into the open part of the U).
- On the top I have nothing, there is a 1/4" gap between the underneath of my marquee box (where some of the speakers are) and the cab - so to install the glass I push it up into this gap about 1 inch and then slide it down into the U channel on the bottom. To remove it to clean or whatever, just slide it up a bit and pop it out.