We have a small dog too that loves to jump at the door. I think this was the first mod I did. I bought the plexiglass sheet at Lowes and the little tool to cut it to size. It was really easy to cut and it just pops into the groove on either side of the bottom of the screen door. They had a few different thicknesses of plexiglass, and I went with a thicker piece (not the thickest stuff, but also not the thinnest). Some adhesive backed Velcro keeps it secure.
I live with fear every day, and sometimes she lets me go fishing.
2015 Shamrock 23IKSS
2008 Ford Expedition EL