The structural covering placed directly over framing members which also serves to transfer loads into the structural framing. Wood structural panel sheathing is commonly sold and installed in 4’ x 8’ sheets.

OSB Sheathing
Oriented Strand Board—Manufactured from waterproof heat-cured adhesives and rectangularly shaped wood strands that are arranged in cross-oriented layers, similar to plywood. This results in a structural engineered wood panel that shares many of the strength and performance characteristics of plywood. Produced in huge, continuous mats, OSB is a solid panel product of consistent quality with no laps, gaps, or voids.
Oriented Strand Board (OSB) is used to sheath lumber joists. The joists are supported by lumber headers. Builders may use bridging to maintain floor joist spacing.
Walls are typically framed with double top-plates. Piping and wiring penetrate the double-top plate.
OSB is stored off the ground on the job site.
Plywood Sheathing
Plywood—Manufactured from thin sheets of cross-laminated veneer and bonded under heat and pressure with strong adhesives. Plywood is also referred to as a "wood structural panel."
Exterior plywood sheathing is fabricated with an overlapping edge to prevent water intrusion into the wall cavity.