Choose between TLL, SNK and HTS-HT by the connection and material first, then check the screw size and exposure conditions. The key differences are the head shape and thread: TLL has a flange head, SNK has a countersunk head, and HTS-HT is a fine-thread woodwork screw particularly suited to wood-based panels.
TLL: a flange head for timber connections
The TLL flange-head timber screw has a broad head that bears on the timber surface. Consider it for a specified timber connection where this head detail is required and a projecting head is acceptable.
TLL is identified as an alternative name for TBS in Rothoblaas ETA-11/0030. Choose the diameter, length, thread penetration and fixing layout from the applicable manufacturer data and connection design. A wide head alone does not establish the joint capacity.
SNK: a countersunk head for a flush finish
The SNK countersunk timber screw is an option where the head needs to sit flush with the timber. Rothoblaas identifies SNK as an alternative name for HBS in ETA-11/0030.
Head appearance is only one part of the choice. Check the timber, member thickness, required penetration and installation instructions. The standard zinc-plated product should not be selected for exposed decking or cladding simply because its head is countersunk.
HTS-HT: fine-thread screws for woodwork and panels
The HTS-HT woodwork screw is a countersunk, fine-thread option for joinery, furniture and wood-based panels. Rothoblaas describes HTS specifically for fibreboard and MDF, with a smooth portion beneath the head and extensive thread engagement.
Do not treat “full thread” as proof that this is the right screw for a highly loaded glulam or hardwood connection. Such connections need a screw and design data suited to the actual application.
Quick comparison
- Need a broad bearing head: review TLL for the specified timber connection.
- Need a flush head: review SNK, checking the material and exposure requirements.
- Fixing furniture or wood-based panels: review HTS-HT and its size-specific installation guidance.
- Fixing a steel connector: use the fasteners specified for that connector. Do not substitute one of these screws on head shape alone.
Outdoor use: check the exact coating and conditions
Our standard TLL, SNK and HTS-HT listings are zinc-plated carbon steel. For an outdoor project, review the exact product's declared exposure limits before buying. TLL EVO and SNK EVO are coated alternatives to investigate, not automatic choices for every outdoor setting.
Coastal exposure, preservative-treated timber and contact with other metals require particular care. Stainless steel grades differ, and a coating classification alone does not prove suitability for a particular timber treatment or salt exposure. Use the manufacturer's compatibility guidance for the selected screw.
Before you order
- Confirm the timber or panel material and both member thicknesses.
- Check diameter, length, threaded penetration, spacing and edge distances.
- Check any pre-drilling requirements and the correct driver bit.
- Check the selected variant's box quantity and exposure specification.
Read our timber fastener spacing guide alongside the exact product datasheet. For structural work, the fixing layout and capacity must form part of the connection design.
Browse timber screws, or send us your fixing details with a drawing or photo so we can help narrow the options and involve an engineering partner where needed.
Supplier references
Rothoblaas ETA-11/0030: screw names and permitted uses and HTS product and technical documentation.
