I have seen here and other places where people have added something to protect their screen door from pets. Here is how I chose to do it:
When looking at my door, I noticed there was a lip across the bottom and the top. This lip is about 1/2 wide. I also noticed there was a channel that ran up both sides of the door and lined up with the lip on the top and bottom. I measured the width and the depth of the channel. It was about 3/16 wide and 1/4 deep. I had a piece of 3/16 plexiglass cut so it would fit into the channel on each side. To insert the glass I simply flexed it in the middle and placed each end into both channels.
To remove it, just flex it. Nothing had to be modified.
When looking at my door, I noticed there was a lip across the bottom and the top. This lip is about 1/2 wide. I also noticed there was a channel that ran up both sides of the door and lined up with the lip on the top and bottom. I measured the width and the depth of the channel. It was about 3/16 wide and 1/4 deep. I had a piece of 3/16 plexiglass cut so it would fit into the channel on each side. To insert the glass I simply flexed it in the middle and placed each end into both channels.
To remove it, just flex it. Nothing had to be modified.