Doors are one of those small decisions that quietly make or break a floor plan. Pocket doors can turn a kitchen and pantry into one beautiful cased opening that closes when company comes over, and a barn door can ruin a wall you were counting on for a console and a mirror. This isn't every door type that exists. It's the ones I actually reach for on residential projects: why I use them, where they belong, and the swings and clearances you need to leave. Free, no fluff, just the stuff I use.