I have a weakness for a denim jacket that earns its keep after September, but only if it can layer over something warmer than a T-shirt. The best version here is not necessarily the most decorated one. SEA's Winslow patch-detailed jacket shows how texture can change the mood without changing the job, while NILI LOTAN's Clement jacket keeps the familiar shape as a clean reference point. Check the shoulder first: if a sweater bunches underneath, the jacket is a spring layer pretending to be an autumn one. Then think about what you already wear below it before buying another jacket that only works alone.

I added a long rail of jackets to the grid below, because fall is when the shape of a denim jacket matters most. ANINE BING's Rory and AGOLDE's Wayne are the easy, slightly oversized ones that fit over a crewneck, Ganni's Structured Denim Fitted Jacket and Madewell's Chore Cropped Denim Jacket sit closer and shorter, and ROTATE's Gathered Denim Jacket is the one with a little drama in the sleeve. LEVI'S Original Trucker Jacket is still the reference everyone else gets measured against. Put each one on over the thickest knit you own before deciding.

My test for this whole formula is simple: can I put it on in a hurry and still feel like myself. A denim jacket and a high-neck layer should make getting dressed easier, not create a costume that only works in a mirror. Soft Goat's Girlfriend turtleneck makes the case for a close, soft knit that stays under the jacket without adding bulk at the shoulder. TOTEME's wool turtleneck goes a little heavier, which only works if the jacket already has room to spare. Let one surface speak, either the jacket's texture or the knit's, rather than asking both to compete.

In 1951 Bing Crosby was turned away from a Vancouver hotel for wearing denim on top and bottom, and Levi's answered by making him a denim tuxedo jacket, presented to him in Elko, Nevada. That is the story usually told behind the look people now call a Canadian tuxedo, and it still sets my rule: if the jacket is denim, the jeans have to look clearly different, in wash, weight or shape.

The easiest version is a dark, rigid straight leg under a lighter jacket. Agolde's Morgan in rinse and the FRAME Vertical are the plain ones I would buy first, and Chloé's lilac high-rise straight leg and Erdem's embroidered pair do the same job with more to look at. For a wider line, Bottega Veneta's palazzo jeans, Givenchy's Cocoon and Saint Laurent's long baggy pair need a cropped jacket, or the outfit turns into one long column of blue. Etro's printed flare and Zimmermann's Valiant flare want a short boot so the hem can fall over it. If you would rather not wear denim below the jacket at all, The Row's corduroy wide-leg pants keep the texture without matching it.

The denim shorts and Versace's striped mini skirt still work in fall with opaque tights and an ankle boot, and DARKPARK's long denim shirt is the lighter layer for a warm afternoon. Hold the jacket against the jeans in daylight before you buy, because two blues that almost match look like a mistake. What I would skip: a mid-wash jacket over mid-wash jeans, unless they were made as a set.

A jacket with visible treatment needs a boot that can take actual pavement, not a second statement competing for attention. Coach's Gigi bootie is a grounded, practical finish that does not ask the rest of the outfit to work around it. Rag & Bone's Mercer sock slingback boot leans dressier, which makes more sense with a plainer jacket and a simple knit underneath. Either way, the boot should read as the outfit's floor, not its headline. Choose texture and heel height based on how far you are actually planning to walk in it.

A denim jacket earns a place in fall only when the rest of the outfit is doing its part, a knit warm enough to matter and a boot sturdy enough for real pavement. The most convincing versions here are not the most decorated jackets, they are the ones with enough room in the shoulder and back to layer properly once the temperature actually drops.

I would test the whole three-piece combination before buying any single piece of it, since a jacket that looks right alone can still fail once a heavier knit goes underneath. Texture is the easiest way to keep the look from feeling like a costume, so let one surface, the jacket's treatment or the knit's finish, carry the outfit instead of piling on more than one at a time. Buy the jacket for the knit you already own, not the other way around. That order is what keeps a denim jacket from being a spring piece worn out of season. If you want to keep browsing, I also put together The Jacket Edit and Sherpa Jacket.