Backbox-Inside

Note the holes in the back panel that allow access to the nuts for securing the mount rails (silver) to the side rails (black).
 
This was with the narrow 100mm x 100mm Vizo mount, later adjusted wider to 200mm x 200mm to fit the much better Samsung.
 
Homemade Top & Bottom Corner Brackets similar to Williams stock 01-9167
1/4 x 20 Carriage Bolts 1" (18 @ $0.07) Home Depot #ADA $1.26
1/4 x 20 Wiz Nuts (18 @ $0.15) $2.70
 
Finished off Backbox with the below stock Williams parts from (http://www.marcospecialties.com/):
(Don't be cheap, like I normally do, buy these custom parts and save the headaches)
 
-Wing bolt - 2 inch (2 @ $3.49) - 3/8-16 thread x 2" 20-9718
-3/8-16 Machine Thread T-Nut (2 @ $0.89) TNUT3816
-Backbox Latch 20-9347 $6.99
-Backbox Toggle Latch Bracket 01-8397 $1.95
-Black Backbox Hinge Set (Pay the Extra for the Raised Flange) 01-9011-R & 01-9011-L $35.00
-Backbox Hinge Bolt - Black (2 @ $.99) 4322-01139-12B
-Cabinet Hinge Pivot Bushing (2 @ $3.79) 02-4352
 
The below stock Williams parts from (http://www.bayareaamusements.com/):
-Lift Trim Plastic - Backglass 30 inch 03-8229-30 $6.95