Exactly Grouse. I have them in all three of my box stands.

Now if you want to go first class, screw a couple of 8" long sections of 2" x 2" wood to the inside walls of your stand - one on the front wall and one on the rear wall, and about an inch below the bottom of the window sill. Put them on the right side for right hand shooters or left side for southpaws. Cut a 1" x 8" plank just long enough to rest on those 2" x 2"s and make a shoothing platform to put a front and rear bag on. Lay your gun in the bags with the muzzle out of the window. Sit back, sip some coffee, and wait for a shot.