Snapfix and Simplefix locators are popular fixing systems for installing sign letters to walls, fascias, and tray panels. Choosing the correct screw size is critical for a secure installation — both in terms of thread size (to match the hole in the locator cup) and head size (to fit within the cup opening).
This guide covers:
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Recommended screw sizes for each cup type
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Suitable fixings for different wall and fascia materials
1. Cup Hole Sizes and Head Clearances
| Locator Type | Hole Diameter (mm) | Max Head Diameter (mm) |
|---|---|---|
| Snapfix Small | 2.0 | 4.3 |
| Snapfix Medium | 3.3 | 7.0 |
| Snapfix Large | 5.2 | 9.8 |
| Simplefix Mini | 2.0 | 4.0 |
| Simplefix Small | 3.3 | 7.0 |
| Simplefix Medium | 4.4 | 8.0 |
| Simplefix Large | 4.9 | 10.0 |
Key rule:
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The screw’s thread diameter should be slightly smaller than the cup’s hole diameter.
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The screw’s head diameter must be smaller than the cup’s head clearance to allow the screw to reach the bottom of the locator cup without splitting the fixing.
2. Recommended Screw Sizes by Cup
Below are common choices using standard countersunk (CSK) or pan head screws.
| Locator Type | Screw Gauge (approx.) | Thread Dia. (mm) | Head Dia. (mm) | Example Screw |
|---|---|---|---|---|
| Snapfix Small | #4 (2.2mm) | 2.2 | ≤4.0 | 2.2×12mm CSK wood screw |
| Snapfix Medium | #6 (3.0–3.5mm) | 3.0–3.5 | ≤7.0 | 3.5×16mm CSK wood screw |
| Snapfix Large | #10 (4.8–5.0mm) | 4.8–5.0 | ≤9.5 | 5×25mm CSK wood screw |
| Simplefix Mini | #4 (2.2mm) | 2.2 | ≤4.0 | 2.2×12mm CSK wood screw |
| Simplefix Small | #6 (3.0–3.5mm) | 3.0–3.5 | ≤7.0 | 3.5×16mm CSK wood screw |
| Simplefix Medium | #8 (4.2mm) | 4.2 | ≤8.0 | 4.2×16mm CSK wood screw |
| Simplefix Large | #10 (4.8–5.0mm) | 4.8–5.0 | ≤9.8 | 5×20mm CSK wood screw |
Tip: Always measure the actual screw head before ordering — manufacturer variations can change head size slightly.
3. Fixings for Different Wall and Fascia Materials
| Substrate | Recommended Screw Type & Plug/Fixing |
|---|---|
| Plasterboard | Use plasterboard fixings (e.g., spring toggles or self-drilling plasterboard anchors) with screws to match the locator size. |
| Brick / Masonry | Masonry plug (red/rawlplug for #6, brown for #8, blue for #10) + countersunk screw to suit cup size. |
| Breeze Block | Use heavy-duty masonry plugs or frame fixings for better grip — breeze block is soft and may crumble. |
| Aluminium Trays | Use self-tapping screws (A2 stainless recommended) with low-profile countersunk heads to fit cup clearance. |
| ACM (Aluminium Composite Material) Trays | Use short self-tapping screws (pan head or CSK) — avoid overtightening to prevent face distortion. |
4. Best Practice Installation Tips
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Pilot Holes: Always drill a pilot hole appropriate to the screw diameter, especially in hardwoods, ACM, and aluminium trays.
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Head Fit: Test a screw in the cup before committing — the head must sit flush to the locator’s bottom to allow the male locator to snap into place.
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Material Considerations: Match screw length to substrate depth; avoid penetrating too far through tray backs, especially if there is illumination in the void.
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Corrosion Resistance: Use stainless steel (A2 or A4) for outdoor signage to prevent rust staining.
5. Quick Screw Selector Table
| Material | Small Cup Screw | Medium Cup Screw | Large Cup Screw |
|---|---|---|---|
| Plasterboard | 2.2×12mm + plasterboard fixing | 3.5×16mm + plasterboard fixing | 5×25mm + plasterboard fixing |
| Brick | 2.2×12mm + red plug | 3.5×16mm + red/brown plug | 5×25mm + brown/blue plug |
| Breeze Block | 2.2×12mm + heavy-duty plug | 3.5×16mm + heavy-duty plug | 5×25mm + heavy-duty plug |
| Aluminium Tray | 2.2×12mm self-tapper | 3.5×16mm self-tapper | 5×20mm self-tapper |
| ACM Tray | 2.2×10mm self-tapper | 3.5×12mm self-tapper | 5×16mm self-tapper |