The second group works differently. Instead of hiding a mattress inside, the back drops down and the seat becomes the bed, sometimes in several positions so it can also be a lounger for reading. These are lighter, easier to move and usually the better pick for a studio, where the sofa gets converted every weekend rather than twice a year.

Mercer41's Naykin is covered in faux fur, which sounds like a lot until you see it in a small cream room, where it looks soft rather than silly. The Zhania from the same brand has six positions, and I would use it as a daybed most of the time. Serta's Lowry and Damon are the sensible ones, and the Damon opens into a twin sleeper for a real mattress feel. Ebern Designs' Meit and Shortridge are both built for small spaces, and the Shortridge is the one I would measure for a nook under a window. Latitude Run's green pull-out loveseat is the pick if you want the sofa to be the color in the room, and their chenille convertible is the softest to sit on.

Two measurements matter more than any photo. First, the depth when it is fully open, including room to walk past it. Second, the height of the seat when it is a bed, because a guest who sleeps close to the floor feels every draft. Check both before you fall for a fabric.

One more thing on fabric. A sleeper gets sat on, slept on and folded more than an ordinary sofa, so I lean toward tight weaves, corduroy, chenille or faux leather over loose linen, which can bag at the fold line. A darker or mid-tone color forgives the coffee rings and the late-night snacks that happen on any sofa that doubles as a bed.

This is the part people skip, and it is the part guests remember. A sleeper with thin sheets and a throw pillow for a pillow is a couch. The same sleeper with good bedding is a guest room.

I keep a full set folded in one basket so it comes out in two minutes. Parachute's Linen Tencel sheet set in garnet feels cool and slightly slubby, and the deep red hides the fact that it lives in a closet most of the year. Kassatex's Laguna stripe linen sheets are the lighter, beachier option. For warmth, Parachute's linen box quilt or matelasse coverlet, both in the same garnet, fold flatter than a duvet and look finished on a smaller bed. If your guest runs cold, Casper's sateen duvet cover or the lighter Hyperlite cover over an insert will do it.

Then pillows. Casper's Original cooling pillows come as a pair, and a real pillow is the single most generous thing you can put on a pull-out. Finish with Kassatex's Mancora alpaca throw at the foot, because guests always want one more layer at three in the morning and never want to ask.

A small tray or a stool beside the bed helps too. There is rarely a nightstand next to a pull-out, and a guest with nowhere to put a glass of water and a phone will balance both on the floor.

What I would skip: a thick foam topper that will not fold back inside the frame. If it cannot tuck away with the bed, it will live in your hallway forever.