Well, looking at these, I can see what a hodge-podge I have!
#1 is the end of the original part of the run. I plan to leave the outside frame. The skinny door, its frame, and the horizontal pieces at waist height will come out. So will the fence/HC that is attached to them. The wood is 2x4s, ripped lengthwise. (To save wood and money; it's plenty sturdy because the metal frame is pretty substantial.)
#2 is the frame for the door that I need to build. It's 24" wide and 5'10" tall. I'm 5'6", so tall enough for me and DH can duck a little. 5'10" is also the length of the vertical pieces in the old door. That door is 21" wide (I don't know why DH made it that skinny! To keep me from putting on weight?) and it's a pain to get stuff in.
Yes, the door needs to be slightly narrower and shorter than the opening. How much? Is half an inch enough? Too much?
Today was also wash day.