You have finally decided to buy blackout shades. Maybe you are tired of waking up with the sun at five in the morning, or perhaps you are trying to create a cozy home theater room where the only light comes from the screen. You picked out the fabric color, you measured your window width, and you placed your order. When the box arrives, you open it up, and you are immediately confronted by a small bag of hardware, a handful of screws, and a mysterious plastic bracket that looks like it belongs on a spaceship rather than in your living room. Do not panic. The single most important step in this entire project is deciding exactly how you are going to mount those shades, and that decision boils down to two simple words: inside mount or outside mount.

An inside mount means the shade fits right inside the window frame, sitting snugly between the two side jambs. This is the look that most people picture when they think of a clean, custom window treatment. The shade sits flush with the drywall, creating a streamlined appearance that allows your trim and molding to remain fully visible. For a homeowner who loves a built-in, tailored look, this is usually the preferred choice. The biggest advantage here is that you keep all of your window sill space. You can still set a plant or a stack of books on the ledge without the shade getting in the way. However, there is a catch. An inside mount only works if you have sufficient depth in the window frame. Most blackout shades require at least one and a half inches of depth to install the bracket properly. If your window is shallow, or if you have old windows with deep protruding stops that eat up that precious space, you might find yourself unable to fit the shade inside. The other tricky part is that your window opening must be reasonably square. If your house is older and your window frame is slightly trapezoidal—wider at the top than at the bottom, for example—an inside mount will look crooked, and more importantly, it will let light pour in through the gaps.

That is where the outside mount comes to the rescue. With an outside mount, you attach the brackets to the trim or the wall above the window, and the shade hangs down over the entire opening. This method gives you a lot more forgiveness. You do not have to worry about the window being perfectly square or having enough depth, because you are basically creating a curtain of fabric that covers everything. If you have a window that is an odd shape or if you are mounting shades on a door, the outside mount is your only real option. The most significant benefit for a blackout shade is light control. Since the shade extends past the edges of the window frame, you eliminate those annoying slivers of sunlight that sneak in around the sides. You can even install the brackets a few inches above the window casing to create the illusion of taller ceilings. The downside here is that you lose part of the window frame; the shade covers some of your trim, which might not be the look you want if you have beautiful woodwork. You also need to be careful that your brackets are anchored into solid wood or drywall anchors, because the shade is going to be hanging off the face of the wall rather than sitting securely inside a pocket.

Once you decide on the mount type, you need to think about the specific bracket style that comes with your shade. Most modern blackout shades use a simple snap-in or pinch-in bracket. You screw the bracket to the window jamb or the wall, and then the shade clicks into place. This is a fantastic system for the do-it-yourself homeowner because it allows you to install the bracket, test the fit, and then pop the shade in without having to hold a heavy roller above your head while you tighten screws. Just make sure you check that your bracket is level. A bubble level is your best friend here. A shade that is even a quarter inch off level will roll crooked and will not fully retract. If you are doing an outside mount, it is helpful to install the brackets first and then actually hang the shade to see how it looks before you commit to drilling all the way. Sometimes you might need to shift a bracket a quarter inch to the left to center the shade perfectly over the window.

Do not overlook the hardware itself. The screws that come in the package are often just long enough to work with drywall or wood, but they can be too short if you have thick trim. If you hit air or if the screw does not bite firmly, you will end up with a shade that falls down the first time you try to pull it up. It is always worth having a small assortment of longer screws on hand. Also, if you are mounting into drywall on an outside mount, you absolutely must use a wall anchor. A blackout shade is heavier than a standard sheer shade, and the constant tugging of raising and lowering it will eventually pull a screw right out of plain drywall. Plastic expansion anchors are cheap and easy to install. Pre-drill your hole, tap in the anchor, and then drive your screw. Your shade will stay put for years.

Ultimately, the difference between a blackout shade that works like magic and one that frustrates you every single morning comes down to those few minutes you spend with the brackets and a screwdriver. Measure twice, check that your surface is level, and do not be afraid to use an outside mount if your windows are tricky. A perfectly mounted shade will block the light, save you money on your energy bill, and make your bedroom feel like a sanctuary. It is worth the effort to get it right.