This doesn't really relate to a problem I have (the screws work just fine), it's more of a curiosity question. Some of the screws I've used recently have a small triangle on their head, as if for lining up something:

enter image description here

I was wondering what this is for, but couldn't really find anything.

What I did find was that bolts commonly have markings that relate to their strength, and screws often have manufacturer markings on their head, but this looks like neither to me.

  • Does the box/packet say who the manufacturer is? Jan 9, 2019 at 14:10
  • A picture of the other end of the screw would help determine if it's there for alignment purposes.
    – B540Glenn
    Jan 9, 2019 at 15:51
  • @chaslyfromUK: Seems like this occurs only on a bunch of screws I had lying around that I don't have a box for. I thought I saw the same mark on the Spax screws I used in the same project, but those have the brand name on their head.
    – Joey
    Jan 10, 2019 at 7:20
  • @B540: The other side looks like the normal end of a standard wood screw. The thread also has no apparent relation to the marking.
    – Joey
    Jan 10, 2019 at 7:20
  • @B540Glenn: Okay, it's a kind of self-cutting wood screw, but the cutting part of the thread is worn enough to be nearly indistinguishable from the normal part of the thread. I've found my answer by searching a bit for answers to both of your comments.
    – Joey
    Jan 10, 2019 at 7:43

3 Answers 3


After reading up a bit on screws of various types I noticed this small snippet in the German Wikipedia:

Von 1967 bis 1992 konnte man die Schrauben anhand einer Körnung am Schraubenkopf erkennen. Seit 1992 wird der Schriftzug (SPAX) in den Schraubenkopf gepresst.

(Between 1967 and 1992 the screws could be distinguished by a punch mark on the head. Since 1992 the "SPAX" lettering is punched into the head.) — horrible translation by me.

It indeed seems to be a Spax screw and a bit worn. The cutting part of the thread is barely recognizable as such and the point is not quite pointed anymore. But other features are still there, such as the part of the head that creates its own counter-sink.

So I guess it came from some old wooden parts and I salvaged the screws. Or whoever. No idea where they came from, they were in my random screws drawers in the basement and just happened to be of the right size for what I needed.

When knowing what to search for one can also find images with that marking:

enter image description here

And it seems that some special-purpose screws still have the old marking:

enter image description here

Well, learned something new about screws, that not all wood screws are equal, and that I didn't even have to pre-drill holes for what I've been doing recently.


Not 100% sure, but this site shows that the triangular marking is brand marking for INFASCO. While I could not find a pozidriv screw from them, here is a bolt with a similar marking. enter image description here


On electrical enclosures the screws have an arrow to show the position of the latch. This looks like a similar indicator so you know when the latch is locked into the frame when the door is closed.

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