Materials:

Four sheets of 3/4" plywood cut to the following dimensions:
Two at 20 7/8" (530mm) by 21" (533mm) and two more at 22 1/2" (572mm) by 21" (533mm)
* It's very important that the width of the top piece (first set of measurements) is exactly as written otherwise you won't be able to fit the equipment in the rack. The second two pieces are the uprights, so if you want the rack to hold more equipment simply increase the second to last measurement (don't forget to get longer rack mount brackets if doing this!).
A sheet of good quality laminate (Italian Black Metallic Ridged is highly recommended) that easily accomodates the above measurements (about 4' by 6' (122cm by 183cm) should do it).
Two 21" (531mm) rack mount brackets (12 space)
One can of environmentally friendly contact adhesive
A small box of screws

Tools you will need:

Power or Hand drill
Assorted drill bits
Screwdriver
Power or Hand saw
T-square
Laminate cutting thing
Router
Cheap or old paint brush

Instructions

First of all you need to find a flat surface that is well ventilated (you'll be creating sawdust when cutting the wood to size, using highly toxic adhesive and shaving laminate). Next you need to cut your wood to size and make sure that everything is true and that all the corners are at exactly 90 degrees.

Then, join all the wood together by drilling pilot holes and then fixing with screws. Make sure you put the longer pieces at the sides and make sure that the inside width is no less than 19" (483mm) otherwise your equipment won't fit.

When everything is all screwed together and nice and straight and true, and all that, you can cut your laminate to size with the laminate scoring thing.

Once it's all cut to size read the instructions on the can of adhesive and stick it all on.

Top Tip - you can stick the adjacent surface pieces on and trim using the router before sticking the remaining pieces on to save time - End of Top Tip

All that remains is to fix the rack mount brackets inside the box and make sure you fix them so that the knobs and buttons of your stuff don't stick out proud of the case (this will help prevent bits getting broken off when you drop it down the stairs or whatever).

The measurements we chose are enough to hold standard 19" rack mountable equipment that also include those 19" deep power amplifiers and some effects processors. If you don't need it for those deep things just reduce the overall depth from 21" (533mm) to 15" (382mm).

If you want your case to hold more equipment simply increase the size of the uprights and the length of the mounting brackets.

To armour your rack just add aluminium edging and corner pieces.

Installing Module Mounting Brackets

Materials:

2 x 19" (483mm) lengths of Aluminum Angle Bracket (1/2" x 1/2" x 1/16">
4 x Self-tapping stainless steel screws (to fit the angle brackets to the mounting brackets)
4 x Self-tapping stainless steel screws (to fit the synth module to the angle brackets)

Tools you will need:

Power or Hand drill
Assorted small drill bits
Screwdriver

Instructions

Make pilot holes in the ends of the angle brackets so that you're able to screw them to the vertical mounting brackets on your rack mount cabinet. Make sure that the angle bracket is fixed behind the mounting bracket lip and that the other flat side is facing upwards.

Once the angle brackets are in place (making sure that there are seven empty holes between each pair of screws) hold the synth module in place and make pilot holes for the smaller screws that will be used to hold it in place.

Easy!

http://www.electronicmusic.com/features/siu/selfhelp/rackmount.html