If you move often, or you are not sure how you will use the room yet, modular is the smartest way to get an L. Each piece is its own seat, so you can build a corner now, split it into a sofa and a chair later, or add a piece when you move somewhere bigger.

McGee & Co.'s Vivienne and Vernon modular L sectionals are designed as corners but come apart easily. Lulu and Georgia's Altman comes with an ottoman you can push against the short side to make a lounger, and the Nelja by Sarah Sherman Samuel has rounded, low pieces that look almost like sculpture. Anthropologie's Celine bundle in corduroy is soft, a little retro and very comfortable. Latitude Run's Kyanne Priyen and their six-piece chenille sectional are deep and plush, made for napping, and Wade Logan's Arregui is a clean, modern corner.

Two things to check with modular pieces. First, how they connect. Some have clips underneath that keep the seats from drifting apart, which matters more than you would think on a hard floor. Second, the arm pieces. In a small room you may want only one arm, or none, so the L feels open.

Modular also makes delivery much easier. Individual pieces fit through narrow doors and up tight stairwells that a one-piece sectional never would, so measure your stairs and doorways before you fall in love with anything.

The third grid is the full corner sectional, two long sides meeting at a right angle. It seats the most people and feels the most generous, and it needs the most careful placement.

Anthropologie's Phillip is a two-piece L that runs nearly ten feet on its long side, made for a big living room. McGee & Co.'s Macy is a little more compact. Lulu and Georgia's Durham has wide arms that double as a place to rest a drink, and the Viisi by Sarah Sherman Samuel is low and relaxed. Anthropologie's Denver Botanica L has a botanical fabric that makes a big piece feel lighter. Jenni Kayne's Harbor sectional is clean and simple, in the soft neutral palette the brand is known for. Wade Logan's Forbestown is reversible, so the short side can go left or right, and Latitude Run's Naomi is a flexible, straightforward option.

Placement is everything with a corner sectional. In a room with walls, push it into the corner that faces the focal point, whether that is a fireplace, a window or the television. In an open room, float it and use the back of the long side as a divider, with a console table behind it. Either way, leave a couple of feet of walkway around the open ends.

A rug should be large enough that at least the front legs of both sides sit on it. A rug floating in the middle of the L makes the whole arrangement look smaller.

What I would skip: a corner sectional facing a wall with the television off to the side. You will crane your neck for years.

I think a sectional is one of the best things you can own if you have the room, and one of the worst if you do not. The shape is forgiving for families, film nights and sprawling, but it is unforgiving about placement.

If you take one thing away, let it be this: stand in the doorway and plan the L so its open side faces you and the long side faces what you want to look at. Then tape the outline on the floor and walk around it for a day. If you trip on a corner or feel boxed in, go modular or choose a chaise instead. The right corner sofa should feel like it opens the room, not closes it.