Blocking is a general, American English term for the use of short pieces (blocks) of dimensional lumber in wood framed construction. Uses include filling, spacing, joining, or reinforcing members. Blocking is typically made from short off-cuts or defective, warped pieces of lumber. Blocking is also sometimes used by people in construction with the sense of a shim or spacer. Names for similar materials in other forms of English include dwang, nog, noggin, and nogging.
Blocking (construction) Wikipedia
Some blocking is used structurally like cross bracing between joists in a subfloor to prevent buckling and stiffen the floor. This use is also called block bridging, solid bridging, and solid strutting.
Fire-blocking is a firestop.
Blocks are spacers between studs such as where an interior wall attaches an exterior wall and for framing corners such as a "three-stud corner with blocking".
Blocking is used for panel edge supports such as sheets of drywall or plywood also called back blocking
Blocking, often called backing or sometimes grounds, also refers to pieces of wood or other material that run between wall studs in order to provide support and attachment sites for mounted hardware or trim such as cabinets, shelving, handrails, vanity tops without a cabinet underneath, bathroom towel bars, mouldings etc. Properly installed blocking is easier to find and use for attaching wall hardware than studs alone. Once drywall, or any other material, covers the wall it can be difficult to find 2x4 studs for attachment, and the position of nails and screws must be adjusted to stud location. Thus, if blocking is installed at a uniform and predetermined height, attachment sites can be found without using a stud finder, and the blocking can be utilized anywhere along a wall at that height. This is particularly useful for installing upper cabinets in kitchens or bathrooms as they tend to be fairly heavy and finding appropriate studs for installation can be difficult.