These provide a flat bearing surface under the head and protrude above the surface. They have a rounded profile which stands up above the surface. They are often used for attaching metal fittings to timber.
Unless otherwise marked, the finish is a clear (silver) zinc plating; ideal for matching hardware, hinges, gate fittings etc. It is moderately corrosion resistant, but the finish is primarily decorative. Steel screws are supplied in grey lube finish.
For superior moisture resistance, check out the stainless screws.
Origin of the Robertson square drive screws
The "Robertson" screws were invented in Canada by Peter Robertson in 1908. Due to patent restrictions they stayed in Canada for many years and became the standard screw in that country. They are now spreading rapidly through the US and other countries. It is a far superior system and we are sure you will agree “once you use them you don't want to use anything else”.
Not only is the drive system better than the conventional drives, the actual quality of the screws is superb. The screws are extremely strong and the square drive means the driver doesn't jump out and the screw does not break under heavy load.