20s tool-free install, 0-trace left No Tools No Drill Design, easily installed in 20 seconds, no drills, screws or brackets required, perfect for tenants, landlords and families, suitable for a variety of wall surfaces, such as wooden walls, tiles marble, etc. Easy installation, making you more comfortable. Although our window shades are designed for drill-free installation, each set includes a complete drilling accessory kit as an additional option to meet diverse installation needs. How to choose the size Women can install it effortlessly, for easiest installation, choose a shade 0.25"~0.5" narrower than your window width (e.g., select 35" width for 35.25" or 35.5" windows). Our spring mechanism allows 0.5" extension, and the height you purchase window height. Note: Requires a window depth of 1.42" to prevent falling.