When kegging homebrew it is very tempting to want to put taps in. My wife wasn't really keen on putting holes in the fridge, even though its beer dedicated, and I can just imagine my 1yr old pulling her own beer but right onto the ground. I decided to use the hanging shelf mechanism to mount taps inside the fridge. It turned out to be relatively simple.
Sides: 2: plywood 1/2"x 3-1/2"x 4"* (give or take depending on your fridge)
Face: wood or plywood 1/2" or 3/4" 3-1/2"x 12"* (depending on shelf depth and shanks) ***see note on step 3
Rear: more plywood 1/2"x 1-1/2"* x 11"* (give or take depending on your fridge)
Shanks: 1-3/4" or 2 1/2" just make sure they're short enough to fit. Also consider getting some with 90 deg nipples. Some short ones have fixed nipples.
Clamps (at least 3)
Fasteners: Nails, screws, etc. for joints (I used a nail gun just to reinforce the glue joints)
1" drill bit, drill
1-1/2" Forstner bit (optional) ***see note on step 3
Spar Urethane finish (is used for high moisture applications but regular finishes and sealers will do just fine)
Bandsaw or jigsaw
Tablesaw (probably optional)
Step 1: Trace Out One of the Shelves and Make a Template for the Layout.
Start by simply tracing out the shelf upside down paper.
Most likely your fridge door shelf is nothing like mine, or maybe it is. The important measurement, to get things to fit, is the distance between the front of the face board and the back of the door(where the back of the shelf would normally meet it). Start with the distance of the front friction point to the back of the shelf (4.5" on my fridge) +thickness of board(.75") -thickness of rear support(.5). I have 4.75" to get the shank and tubing in. You may not have to subtract the thickness of the rear support if it won't come in contact with the beer lines.
Look at the points that hold the shelf to the door. Mine was very similar to a french cleat where the front is held in place by interlocks in the rear of the shelf. I marked out where the critical friction points are after tracing it out. As long as you get those right it will stay put.
There is probably an odd angle to the shape of the shelf too. The interlocks on the wall of the door don't stick out very far so incorporating the angle is pretty necessary in my case. I found it was 85.5 deg. This is a pretty easy cut to make on any table saw.
When laying out I decided to use dadoes for the front joint. This way I could make a strong enough joint without putting fasteners through the front. The joints on the rear support don't really need to be a super strong joint. The rear support basically pushes the side pieces into the corners keeping then on the rear cleats. Just a glued edge and some nail brads should be fine.
Step 2: Cut Face to Length and Layout Sides
Cut the face to match the width of the shelf.
Lay it on top of the shelf or template and mark out where the sides will make the outside of the joint. Draw out the dado. Use the thickness of a plywood side to mark out the approximate width of the dado. At this point you should mark out where you want holes for the shanks to be as well.
If you don't have the ability to make a dado (have a table saw or hand tools, etc), these lines will just be where you fasten the sides with glue and screws. You will still need a way to make angled cross-cuts on the sides. Most bandsaws and jigsaws will do this. Another approach may be to use hinges for the joints.
Step 3: Cut the Dado, Cut Sides to Length, Cut Rear Support
Cut the dado at the appropriate angle (if you can't make the dado joint cut the very ends of the side pieces to make the correct angle.) Now do a dry fitting on top of or under your shelf.
Since you know the space between the two side pieces, this is a good time to lay out, drill out and fit the shanks into the face.
***If the face is 3/4" thick and the shanks are the 1-3/4" size you may have to drill a large 1 1/2" recess for the nut. This requires the forster bit. Other solutions are to use either a 1/2" thick face or a longer shank and or a 90 deg nipple but space is very limited behind the shank. There are many solutions. Just make sure it fits before hand.***
When everything looks good with the dry fit, mark the length of the sides and cut them down using the same angel as the front dado or face joint so the ends are parallel to the face.
Now place this back under your shelf or on the template and lay out your rear support length. Cut the rear support to length using the same angle as before.
Before cutting the cleat in the next step, try fitting dry fitting this in your fridge door to get it just right. Make sure the face is flat against the outer friction points with little wiggle room. This is where a few loose brad nails will help hold things together for a few min until the fitting is done. I had to trim/sand off the outside rear corners to fit them into the rounded plastic corners in the door.
Step 4: Lay Out and Cut Out the Cleat From the Sides.
Measure and layout the important friction points of the cleat first. Then freehand the rest of the cut lines. I went though a couple of layouts before committing.
One trick to bandsaw them both out at the same time is to brad nail the two sides together, cut and then separate. Just make sure to put the two pieces face to face or back to back to make things symmetrical.
Step 5: Glue Up: Clamps, Clamps, Clamps, Clamps and Finish.
This shape can be awkward to clamp but one method is to clamp a long scrap about the same width but longer than the rear to the rear support. (First place some plastic in between as a glue barrier though.) This will allow you to really only need two more clamps to hold the whole thing together. You can never use too many clamps though.
Finish/sealer is a must since this is going in a damp fridge. Spar Urethane is good choice but any sealer will do.
Step 6: Mount and Enjoy!
Now just mount it in you fridge with taps and beer lines. Relax. Have a homebrew.