Blocking (construction)

The primary purpose of blocking is to brace longer frame members to help resist buckling under vertical compression.

Blocking also resists the rotational movement, or twisting, of floor joists as they deflect under load.

[2] When correctly placed, blocking also provides grounds (also backing or back blocking) for supporting the cut ends of wall claddings and linings or for attaching items such as cabinets, shelving, handrails, vanity tops and backsplashes, towel bars, decorative mouldings, etc.

Properly placed grounds make the second fixings easier once the walls are lined and they distribute the weight of heavy items across structural members.

[4] [5][6] Blocking is typically made from short off-cuts or to make use of defective, warped, pieces unsuited for use in longer lengths.

Solid “bridging” to stabilize floor joists .
Blocking placed as attachment points for cabinets, while doubling as bracing against compression of the studs.