Normally there's a slit at the bottom, but this one doesn't have one.
note from PPS:
Removing the end cap will be the hardest part. Here is how we do it.
You will need a 3/8-24 bolt , two nuts and two wrenches.
Screw the bolt into the cap with the two nuts. Tighten the bottom
nut onto the cap... then lock that nut into place with the second nut....
You will need two wrenches.... One to hold the nut onto the cap and
the other backs out the nut... If your lucky,,, the cap will back
out with your bolt assembly.