The rubber channel thing is super easy to make. Alternately you could simply glue it using weatherstripping adhesive (neat and tidily) Or use screws or use plastic rivets or....
Do you have any of the old T post? Just measure off that. The pillar is 90 degrees to the sill piece, so you can put a square on it to get it in place.
Do you have any of the old T post? Just measure off that. The pillar is 90 degrees to the sill piece, so you can put a square on it to get it in place.