Raycast only shooting on certain layers?

I'm making a Portal clone, and I have a code that is supposed to shoot only onto objects with certain layers. I start by defining the variable:

Later in the script when I incorporate raycasting:

I created two layers: "Shootable" and "Nonshootable." I put the layer "Shootable" on the objects I want to be able to shoot onto, and...

Raycast only shooting on certain layers?