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What is a square or ‘Robertson’ screw drive design?


What is a square or “Robertson”
screw drive design?

  Two screws with a square drive  

A square-shaped drive that tapers towards the screw’s shank.

  Square drive from below  

A square drive as viewed from above.

  Square screwdriver bit  

Which screwdriver bit?

A screw with a square drive is designed to be driven with a square screwdriver bit. Ensure you select the correct size bit for your screw.


For more information, see section: How to select the correct screwdriver bit for the screw.





  • Provided you use the correct size, a screw with a square drive will fit snugly on to the end of a square screwdriver bit, and will stay there unless you pull it off. This means that you don’t have to hold the screw against the bit when driving it in

  • Compared to the slotted design, the square design allows the screwdriver bit to sit more securely in the screw’s drive, meaning there is less chance of it slipping out and damaging the screw or work surface


  • Because a square screwdriver bit must fit exactly into a square drive, a bit that is even slightly worn will struggle to turn the screw. As a result, using screws with square drives may prove costly if you have to keep replacing bits


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