In the small-mammal house at the National Zoo, handprints tell the story. Without the glass, sticky hands belonging to second-graders would come in range of the meerkat. The big-eyed, fuzzy meerkat, which, according to Zimbabwean legend, can kill both cattle and men who wander too close.

At the zoo, glass is a protector. It protects the animals; it protects us, too, shielding the wind while we have a quick sandwich in Chinatown or wait another 15 minutes for the X2 to finally roll down H Street NE. Glass keeps us climate-controlled on our late-night bike ride at the gym, going nowhere, then going home to dinner, TV, and bed.

Behind glass, we watch our ’91 Toyota roll through the checks at 1001 Half St. SW and—mercifully, shockingly—pass inspection. We sit at a restaurant window on Connecticut Avenue NW and count passers-by: One in five is not on a cell phone while walking south from Dupont Circle, eyes ahead, not looking at you looking at them.

Glass allows the sun in, even on lobbyists in drab office buildings on K Street. It lets us peer into the carryout chicken joint in Mount Pleasant and decide if we want to go in or go home and cook. It frames racy lingerie and shoes we can’t afford in Georgetown; it advertises the living-room services of our neighborhood psychic.

Every day we walk by the same windows, the same empty storefront with the duct-taped glass, the same cigar-store Indian, the same sacred heart of Jesus on a T-shirt. Sometimes we even remember to look.