The diagonally placed holes are for the machine screws and wing nut that will eventually hold the two pieces together. If you are using ¼ inch hardware like I specced above then the holes should be ¼ inch. Note that you probably want to cut the bar first then stack the bars and drill the holes so that everything lines up later.
The 3 sets of perpendicular holes are ⅛ inch and are for the zip ties that hold the vinyl tubing in place. Make sure you have zip ties that fit.
Finally use a file to clean up the burrs from the cut and the holes, and round the corners slightly to cut down on the jabbyness of the pieces.
Bending the Bracket
There is not an exact plan, just follow the picture above. The general goal is to create spring like tensions with the curves.
I bent the ¼ Inch aluminium stock using a combination of my hands, a vice, a pipe and a hammer. The bar was wrapped or hammered over and around the pipe to make the bends One thing that you should pay attention before you make the bends is the way that the holes that will hold the pieces together are lines up. Once you have the pieces bent , assemble them with the machine screws and wing nuts. Note that you can adjust the tension by disassembling the bracket. tweaking the bends and reassembling.
The Rest of the Assembly
Well at this point you are 75% there.
Cut the vinyl tubing into two 3 ft pieces and attach it to each end of the primer bulb, using your hose clamps. Paying attention to the flow of the primer bulb pump. Attach the tubing to the bracket using zip ties.
The end that goes into the supply water needs something to keep the end of the hose weighted down. I used a piece of ½ inch 90 degree PVC connector. The hand washing stations that you can purchase appear to use fuel filters that fit on the ⅜ inch hose. Anything that sinks in water and can be attached to the end of the hose works.
To increase the longevity of the primer bulb / pump you will want to keep it off the ground by attaching it to a board. I went one step further and built a hinged housing with some 6mm corrugated plastic that I have plenty of.
That’s it you should be good to go. Note that the parts used to make this (specifically the primer bulb and the fuel filter if you used one) are NOT food safe, so this is not designed for dispensing drinking water or any other beverages.