Review on NAMSAN Pet Screen Door - Lockable Sliding Doggy Door, Inside Size 12x16 Inches, Cat & Dog Entrance, Automatic Closing by Stacey Bradley

I put it on a glass porch so my dogs can get into the fenced yard. Since I couldn't remove the screen for assembly, it was probably more difficult than if the screen could be placed on a hard surface. In the end, one person from the outside pressed a piece of plywood against the screen while another person inside the screen tapped the inside edge with a rubber mallet, trying to install the pins that held the two sides together. It was very difficult at first to line up the two sides exactly so the pins were in the right places when trying to set them. While it wasn't easy once installed and all the pins snap firmly into place, it's sturdy and even my stubborn (and blind) herding dog couldn't pull it off. All my dogs are small to medium sized and fit in well. It was installed in the bottom corner as close to the edges of the screen as possible, like the picture in the listing. Aside from the difficulty installing it, it was a great product that made it safer and more comfortable for my dogs to go outside when they wanted to.