A slab door is a standalone door without a frame or hardware. A prehung door is a complete set that includes the door, frame, hinges, and sometimes the doorknob and lockset.

In most cases, a prehung door is the better and easier option to install, especially for DIY projects or exterior applications, as they often come pre-weatherproofed. They require fewer tools and less experience to install properly. Although prehung doors are heavier and have a higher upfront cost, the investment is often worthwhile for a complete upgrade that includes a new frame.

A slab door may be a better choice if you are on a tight budget, have a custom-sized wall opening, or only need to replace the door while keeping the existing frame. While the initial cost is lower, you will need to purchase all the hardware separately and do more DIY work to hang it, which may not result in significant time or money savings.

You can use any wood to make an interior door, provided it’s the right thickness. Common options for painted doors include pine or poplar for the stiles, rails, and mullions, and paint-grade plywood for the panels. You can also opt to make your own panels out of pine or poplar if you intend on staining the door instead. Opting for oak, maple, or another hardwood is another great option for a high-end door that will last for decades, but the wood will cost significantly more.

If you’re installing a pocket door into an existing door opening, the new space will need to be twice the width of the existing door, plus an inch. You'll need to double that number if you’re adding dual pocket doors.

Most modern door knobs will all fit in standard, modern doors, so if you know your door was made in the last 50 years or so, you should be fine buying a standard replacement door knob. The only exception would be a thumb latch handleset for an exterior door, as this type of door knob may not fit your door without drilling a mounting hole for the bottom of the handle. Antique or custom doors might also have different sizes and knob mounting holes, so call in a professional if you don’t believe your door is a standard one.