The top spring-loaded adjusting section of the Ideal Patio Pet Doors appears as an "H" piece when viewed from the side. The overall width of this piece is 13/16" (Will fit into most any sliding glass door track).
The spring-loaded adjustment provides for a 2 1/2" range for proper fitting into your opening. Most top tracks in sliding glass doors do not have any center rails, however, if you do have this feature then the Ideal Patio Pet Door can straddle any rail at the top 5/8" wide or narrower.
The spring-loaded top is secured with 2 thumbscrew locks, accessible from inside the house only, so that someone from the exterior of the house would not be able to compress or remove the unit.
The bottom section of the Ideal Patio Pet Door has an overall width of 5/8". A semi-circle, "C" channel is centered and runs the length of the bottom. This "C" channel is design to straddle the center rail in the channel on the floor that your sliding glass door follows.
By straddling this center rail, the Ideal Patio Pet Door will remain centered to the frame of your sliding door when closed to this unit.
Note:If the center rail in the channel on the floor is wider than 5/16", then this patio Insert will not be able to straddle it and as a result may not fit properly in your opening.