The vocabulary that shows up across home-improvement projects.

Plumb — perfectly vertical.
Level — perfectly horizontal.
Square — at a true 90° angle.
On-center (OC) — spacing measured from the center of one member to the next (e.g., studs 16″ OC).
Stud — a vertical framing member in a wall.
Joist — a horizontal framing member supporting a floor or ceiling.
Kerf — the width of material a saw blade removes.
Miter — an angled cut, often 45°, for joining corners.
Shim — a thin wedge used to level or fill a small gap.
Countersink — a recess so a screw head sits flush or below the surface.
Pilot hole — a small pre-drilled hole that guides a screw and prevents splitting.
R-value — a material’s resistance to heat flow (insulation rating).
Load-bearing — a wall or member that carries structural weight.
Flashing — material that directs water away from a joint or seam.
Toenail — to drive a fastener at an angle to join two members.

Frequently asked questions

What does “on-center” mean? Spacing measured center-to-center between framing members.

Difference between plumb and level? Plumb is vertical; level is horizontal.

What is a kerf? The slot of material a saw blade removes as it cuts.