How do you use these Plasplugs screw gauges? Why are they teardrop-shaped?

[AVR2]

This is probably a very dumb question, but I'm uncertain why the screw gauges on this strip of Plasplugs are that elongated teardrop shape.

Is the idea that the slot for (say) the 5mm plug is sized to indicate the maximum and minimum thicknesses of screw thread that can be used with that plug size?

 

[Burnerman]

The round holes are for you to measure your drill size, the elongated ones are to check the screw diameter.....if the shaft fits in there then the plug and screw will hold.
That's what I've always assumed, but never actually used it!
John

 

[AVR2]

Yes, the round holes for the drills are obvious, it's the teardrop shapes for the screws that seemed odd.

 

[JohnD]

yes, there are various sizes of screw the plug will accept. The biggest acceptable fits the wide end of the hole, and the smallest acceptable fits the narrow end.

Anything between the two will fit.

The bigger drill sizes fit a range of bigger screws; the smaller drills fit a range of smaller screws.