Shower Doors Are Difficult to Open?

First, make sure you don't have a calcium build-up in the running track from hard water deposits or a small sliver of soap or a hair clog stuck in there. If that is clear, then try some WD-40 sprayed right in the track. Work the door back and forth several times and see if that makes any difference. Also, one other thing to check is to make sure the shower door is seated in the track correctly.

You can try rubbing either a bar of soap or an old candle on the track. I used a candle on the track of a stubborn sliding door and it works great!

Clean the doors and runners with vinegar to remove calsium and minral deposits. Then either run parafin wax along the runners both top and bottom several times or use a clean bar of soap.