Rain Pants

I have never found it useful to use ankle zips. You are just distributing the muck on your soles throughout the inside of your pants. I don't get it. If someone can explain it better I am open.

On some pants, the ankle slit is on the inside (the medial side) and on others, it is on the outside (the lateral side). If there are zippers, snaps, or velcro for closure, they will see more abrasion from the other leg if they are on the inside, but they are a lot easier to reach for wearer adjustment if they are on the outside.
Which is better?
–B.G.–

There are several rain pant patterns that eliminate the outseam to eliminate that source of leakage. In that case you would use the inseam for a zip. "The Green Pepper" has some inseam only patterns.

I've had several pants with ankle zips, and none of them would allow donning over hiking shoes with chunky soles. I vote no on the ankle zips, yes on adjustable hems.

"Commonly, rain pants will have a slit up the inside of the leg to the knee, and this is used for going on over boots. The slit has to be closed."

Use a gusset, and velcro at the ankle.

I have found it lighter and more waterproof to just make the legs wide enough to allow shoes to fit through. Then a little bit of velcro will allow you to close off the bottom if you want to.

I'm now using homemade silnylon chaps, and they work far better than anything of comparable weight.

The advantages:
Easy to make
Lighter than pants (and much lighter than wp/b pants allowing comparable ventilation)
Good ventilation (feels better than GTX pants)
Easy to put on (wide enough to go over shoes)

Disadvantages:
Works only with a long jacket (I made mine to match) or poncho
Less protection in high winds

Do you have any pictures? Are there instructions online?

I have been thinking about making rain pants as well. I would like to have them for hiking & biking. The only problem is the posterior may be a bit slippery with the sil. I have some old heavy rains pants I may sacrifice for a pattern. I think just about any pant pattern would be a good place to start. You can get an idea of what you need to cut and tweak it for better fit.