Bottom inverted U shaped, spring loaded guide or retainer.

Unknown manufacturer sliding screen door which, at the bottom or base of the slider, has inside the door a full door width plastic spring pressured inverted U shape device which fits over the fin on the threshold which faces up. To remove the door one must press this device up into the door while slowly pulling the door off or away from the threshold. Nothing in your catalog that I could find resembles what I need for three doors and I need to replace them as they are ten years old are deteriorating. Each of the three is 34 and 1/2 inches in length.
.