Timberlok railway sleeper screws from Railwaysleepers.com
Sleeper Screws Hex Washer Head Green
SleeperFit Official Black Timber Railway Sleeper Framola Pergola Screws - Extra Clamping 8mm Hexagon Flange Head - Torque Magnetic Driver Bit (Pack of 50) (6.3 x 65mm) : Amazon.co.uk: DIY & Tools