PROpad was designed to accompany Capture on any belt or strap, including vertical backpack straps. On a backpack strap, PROpad adds extra stability and comfort, particularly on backpacks that have thinner, less rigid straps.
Note that when wearing PROpad on your backpack, you're definitely going to want to replace the standard clamping bolts on Capture with the long clamping bolts.
Swivel Capture open and stick the open end of the backplate through the side slot on PROpad.
Not really another step, just keep doin' what you're doin'. We just want you to make sure the Capture backplate is going through the side slot and not in front of it.
Push the backplate through until the clamping bolt sticks out on the other side of the PROpad side slot.
Now take the entire setup - Capture and PROpad - and place it entirely behind your backpack strap.
Capture's clamping bolts should straddle either side of your backpack strap as shown.
Swivel Capture shut over your backpack strap and tighten the clamping bolts until Capture and PROpad are securely clamped to your backpack strap. If you have trouble swiveling Capture shut, loosen the clamping bolts first.
Viola, you did it. Clip your camera in and feel the difference in stability and comfort!