Actually, all you'll see is a dense object. If someone puts explosives in their luggage the x-ray will not tell you the operator that there are explosives in the luggage.

This focus on shoes is just plain stupid. And I'm not talking run of the mill, fell out of the stupid tree and hit every branch on the way down stupid. I'm talking about stupid to the point where someone has drawn a circle for the person in charge of harassment at the TSA and this jackass keeps insisting it's a square. I'm talking about a person so stupid it's a miracle they make it out of the house without assistance by at least three other people.

I can smuggle explosives past the so-called security at the airport at will. That's right, any time I or anyone else wants C-4 or any other non-metalic explosive (and most are non-metallic) airside, they can do so. Why? Because your agency is so incredibly stupid thinking that shoes are the only place that passengers could ever hide explosives that they fail to realize or care that plastic explosives are malleable. A volume of explosive that will take down a plane and more will easily fit in a person's undergarments or in their body cavities. These explosives will also fit and go unnoticed in carryon baggage unless someone puts wires and a blasting cap there too.

Don't believe me? Your x-ray tests are done so that your employees will pass them and Congress won't send your agency back to the streets where most of your employees belong. If someone takes some PETN and molds it carefully, the operator of the x-ray won't give it a second look. It's just another one of thousands of dense looking objects that bored x-ray people see every day. MAYBE if someone shaped it into one of those cute bomb looking devices on that ridiculous sign at the checkpoint and stuck some wires and a clock around it, a screener might notice it, but even that is a real reach.

Congratulations on knowing what a shoe looks like under the x-ray. Guess what? The explosives aren't there.