Outer width does not define the entire geometry
Knowing box-section outer width and height does not establish usable internal clearance. Wall and internal corner radius constrain an inserted component. On a U channel, clarify whether web and flange dimensions are internal or external. Specify clear distance between mating faces separately where it matters to assembly.
Clear dimensioning also defines incoming acceptance. An outside-size tolerance on a drawing does not automatically create the same internal-clearance tolerance. Distinguishing functional dimensions from general outer dimensions aligns quotation and incoming inspection.
Rolling, bending and extrusion are different routes
Depending on material and geometry, a section may be rolled, formed from sheet, welded or extruded. These routes can change corners, seams and tolerance approaches. Equal outside dimensions do not make every route acceptable as a substitute. State any manufacturing route required by the project.
For 6060 and 6082 aluminium profiles, appearance, mechanical requirements and temper are considered together. A stainless section may instead prioritise weld seam, finish and environment. Define production route separately from alloy identity; one designation does not supply all the other requirements.
When will the finish become final?
Share visible-surface, anodising, grinding or protective-film requirements as early as dimensions. Seam position or bending marks can affect appearance and assembly. Later drilling, milling and cutting also determine which section surfaces provide manufacturing references.
A bright surface alone does not establish straightness or flatness. Twist, bow and end-cut condition can be separate checks on long sections. Define acceptance length and method through the applicable standard or agreed drawing requirements.
An enquiry that shows the function
Do not limit a special-section enquiry to the words U or box. A section drawing, measurement references and required assembly clearance speed assessment. Provide material, temper or delivery condition with length, quantity and finish. If a standard section is unavailable, an alternative route is assessed separately and does not automatically change drawing requirements.