my kirby heritage.

[aaron158]

its a square shaped head. they were invented in Canada there more popular here but they can be bough in the us to just harder to find. people who build homes prefer them over phillps screws because they are much harder to strip.

 

[human]

So that's what they're called...

I don't think I've ever actually seen a Robertson screw but I have a couple of bit sets for drills and screwdrivers that have those square bits. I always wondered what they were. Torx and hex screws are definitely more popular here in the 'lower 48'.

 

[aaron158]

there's also an American knock off version of them call square recess the knock off version is a bit different it is just a plain screw were the genuine Robertson version has a tapper to the square witch has an effect to it that locks the trip of the screwdriver into the head of the screw.

with u have both a genuine Robertson screw and screw driver u can insert the tip of the screw driver into the head of the screw and hold it upside down by the screw and the weight of the screw driver will not make it fall out.

one of the ways to know there genuine Robertson is the screwdrivers or bits are normally colour coded for easy side identification. like #0 yellow #1 green #2 red #3 black.