RHS in cold and hot finish. Mild Steel Rectangular and Square hollow section, also called box section. Can be supplied in various grades including BS EN 10025 S355 and S275. Mild Steel Rectangular Hollow Section Mild Steel Square Hollow Section. Call 01902 716333 for nationwide delivery of mild steel box section. A hollow structural section (HSS) is a type of metal profile with a hollow cross section. The term is used predominantly in the United States, or other countries which follow US construction or engineering terminology. HSS members can be circular, square, or rectangular sections, although other shapes such as elliptical are also available. Rectangular Hollow Section|Wellmade Wellmade Scaffold Produces Rectangular Hollow Section(RHS),Circle Hollow Section(CHS),Square Hollow Section(SHS) in Painted and Galvanized for Construction Formwork Concrete Yoke and Scaffolding Frame Raw Material in All sizes and Customized. Sizes of Rectangular Hollow Sections range from 50mm x 20mm x 2.0 wall thickness up to 300mm x 200mm x 9.0mm wall thickness. Standard stock lengths are 8 mtrs - 6.5m or 12 m are available in some sizes.