I need to choose the right screws to install a child window guard into a wooden window frame.

The guard comes with one-way screws, but my 9 month old hasn't figured out the trigger on my Dewalt, so I want to use normal screws. I called the manufacturer but they are "unable to recommend screws other than those provided."

The screws look like 1" #10 sheet metal screws with either pan or truss heads (also below). This is a little odd because they recommend them even for wooden window frames.

The guard is constructed of square steel tubes with 3/8" holes on one side and 3/16" holes on the other (see below). The screws attach the guard to the window frame by passing first (and entirely) through the 3/8" hole, the threads and shank pass through the 3/16" hole and into the frame, and the head presses up against the inside of the tube around the 3/16" hole.

Screw heads Screw transverse Guard tube

If this were any other application (i.e. one that isn't for preventing my child from falling to his death), I'd just get a round-head wood screw and call it a day. Instead, I don't know how to decide between:

  • Round-head wood screw (since it's going into wood)
  • Truss- or pan-head sheet metal screw (since that's what they provided)
  • Roofing screws (since they are designed for attaching metal to wood)
  • Something else I haven't thought of

What say you, oh wise DIY Stack Exchange?

-- Sal

  • 2
    Use high-security Torx screws. Nobody's going to sell those bits to an infant. Oct 4 '17 at 4:02
  • Are these screws on the inside? If so, I cannot see why these "one-way" screws would be necessary fir this application. Is the infant an escape artist? I would replace them with regular ones (Phillips or Pozidriv, slotted, etc., etc.) of the same size. resources.tannerbolt.com/articles/what-type-of-screw-is-this Oct 4 '17 at 11:50
  • I hope your child does not get the chance to discover that a finger fits in the chuck at the same time they figure out the trigger :( Oct 4 '17 at 12:48

Round-head wood screw


Truss- or pan-head sheet metal screw

Either one will work fine. The stresses on that screw would likely be minimal and would be tensile rather than shear, so use whichever one is easiest to find in a 3/16" (#10) diameter with a head that fits through the outer hole.

  • 3
    Note: the wood you are screwing into and the size of the pilot hole you drill are more important considerations when it comes to "pull-out" strength. Oct 4 '17 at 4:03

The manufacturer is being a little ridiculous, on the face of it.

Those one-way screws were invented to prevent thieves from easily unscrewing things and stealing them. They have zero bearing on the holding power of the screw.

The company are protecting themselves from litigation. Having said that, if you don’t use their screws and something goes wrong with the window guard, your warranty may be void or you could even be found responsible for the failure in a court. Stranger things have happened.

Personally, I would just use quality screws with a torx or square drive head.

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