Hollofast
Blind fastener for steel HSS · One side. One tool. Structural strength.
A high-strength expanding-sleeve fastener engineered for square, rectangular, and round Hollow Structural Sections. No internal access, no welding, no specialist equipment — just a pre-drilled hole and a torque wrench.
- Diameters
- 4
- Clamp ranges
- 3
- Finishes
- 3
One-side access
No internal access to the HSS section required. Works on fully sealed structural hollow sections — square, rectangular, and round.
Standard tooling
Installs with a standard torque wrench or impact driver. No specialist equipment, drill press, or hot-work permit needed on site.
Structural rated
Verified tensile and shear load ratings. Factor of safety 5:1. All connections must be confirmed by a qualified Structural Engineer.
Engineered for HSS connections
A faster, cleaner alternative to through-bolting and site welding — without compromising structural performance.
Fig. 1 — Hollofast dimensions and installed cross-section
- Single-side installation — no access to the inside of the HSS required
- No welding or specialist drilling — reduces hot-work permits and on-site hazards
- Fast install — insert into pre-drilled hole and torque to spec with a standard wrench
- High safe load capacity — M10 to M20 (3/8" to 3/4") for light framing through heavy structural connections
- Three clamping ranges per diameter — accommodates varying material stack-ups without changing fastener type
- Three corrosion protection options — Zinc, Hot Dip Galvanized, and Stainless Steel 304
- Compatible with square, rectangular, and round HSS
- Hexagonal head — installs with a standard torque wrench or impact driver
- CAD drawings available — 2D and 3D files for detailing and submittal packages
Four steps to a structural connection
No special skills beyond a standard torque wrench. No through-access. No hot-work permit.
Drill the hole
Drill a single clearance hole to the specified diameter from one face of the HSS only. No through-access required.
Insert Hollofast
Thread the connecting plate or bracket onto the Hollofast and insert the assembly into the pre-drilled hole.
Torque to spec
Apply the specified torque with a standard wrench. The sleeve collapses inward, gripping the inside of the HSS wall and developing full clamping force.
Connection set
The fastener is fully set. Verify torque with a Structural Engineer sign-off as required for your project specifications.
Full product range
12 product codes across four diameters and three clamping ranges.
THF-1-12 in stock — Zinc & HDG. Immediate dispatch.
Safe Working Loads at Factor of Safety 5:1. All connections must be verified by a qualified Structural Engineer. Code format: THF-[Size]-[Diameter]-[Finish] — e.g. THF-1-12-G = M12 / Size 1 / Hot Dip Galvanized.
Find your fastener
Pick your diameter, clamping range, and finish — get the product code and load ratings instantly.
Three corrosion protection options
Specified to suit the exposure environment of your project.
Zinc plated
Code suffix: -Z · In stock THF-1-12
Standard corrosion protection for interior or mild exposure environments. Most cost-effective option for sheltered structural applications.
Hot dip galvanized
Code suffix: -G · In stock THF-1-12
Superior protection for external, high-humidity, or industrial environments. Recommended for exterior structural steel exposed to weather or aggressive conditions.
Stainless steel 304
Code suffix: -S · Available to order
High corrosion resistance for demanding outdoor, chemical, and marine-adjacent industrial applications. Maximum durability in aggressive environments.
Get a quote
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For stock orders, project quantities, technical questions, or CAD files — reach out directly or use the form. We respond within one business day.