We have two cats who absolutely love looking out our big kitchen window. (They are indoor cats so sitting on a window sill is the closest they get to being outside). They would sit on the kitchen counter or on the table and sometimes try to fit on the sill. They are inseparable so sitting next to each other on the tiny sill was impossible. I bought the kitty sill and attached it to the wooden kitchen window sill first with the velcro to make sure my cats would use it. As soon as I put it up, they hardly ever left it. After a few days, the sill started to sag a little (I'm sure because both of my cats would always be on it at the same time) so I decided to use the screws and attach it that way. I was able to use a 1/16th drill bit to drill the holes in my sill and then used the screwdriver to manually screw in the screws. The installation took me less than 5 minutes and now the sill is totally solid. My cats LOVE this product and I would absolutely recommend it!