I bought all the materials for this project for $17.13.
What you'll need:
1 iron pipe 3/4" (cut 1/2 inch shorter than doorway)
4 corner braces 3 inch
4 nylon spacers 1/4 inch by 1/2 inch
4 #10 washers
4 #10-32 3/4" machine screws
4 #10 nuts
8 taper head screws 3 inch
Adjustable wrench, or 3/8 inch open end wrench
Two tapping blocks
Drill w 5/32 bit
Step 1: Build T- Bracket
Do not fully tighten the screws yet, since the movement will make it easier to insert the assembly into the pipe. The .26" inner diameter of the nylon allows some play, so you will want to get it square before the final tightening
Step 2: Insert T Brackets In Pipe
Put the empty end of the pipe on one tapping block and use the other block with the hammer to drive in the bracket.
Do the same on the other side, but be careful not to bend the bracket (hit it squarely).