[rjsimmon]

That is only on the AV-8B.

The F/A-18 Martin Baker seat has two 'horns' on them that fracture the canopy.

[TMSuchman]

There are more than that, take a close look at the rest of the aviation fleets.
Sometimes the det. cord is in the rails that attach the canopy to it’s frame/s. That one of the first things we worry about when safe ting a ejection seat after a “hard” landing, The pins installed interrupt the ejection process/s at varying points of the ejection system/s.