Step 3: Installation
Measure your A/C from left to right including your frame. Cut two pieces of the C-channel in both sizes1/2" and 3/8". In the 3/8" C-channel insert nut rod coupling on the end. Drill hole on the side, through channel and coupling, than insert a screw. Make sure it's flush on both ends, since 1/2" channel has to fit over it. Refer to pictures.
Measure your window from top to bottom. When you measure, make sure you measure inside of the frame. Your C-channel has to fit inside of the frame. It's very important, since this is going to be holding part of the weight. Cut both C-channels 1/2" and 3/8" to the measurement you got.
Place your A/C inside of your window frame and slide it in to the side frame as far as you can. If the frame around A/C is well attached, you shouldn't worry about it falling out.
Insert the vertical 1/2" C-channel, and drill a hole right about where your horizontal channel with the nut coupling meets. Screw the two together. Also, at this point you might want to screw your C-channel to the frame around the A/C unit.
Insert the 3/8" C-channel inside of the 1/2" and close the window. This will push them together, allowing you to see where the gaps might be. Screw your C-channel in place using self-drilling screws. You will have to drill through window frame. See pics below.