It's surprising at how little this matters.

I came back from a tech event once with a build a robot kit, except I'm a very light packer and the box was huge so I had to take everything out and fit it into a backpack along with everything else I had.

I had a compartment that had an assortment of circuit boards, screws, wires, plastic pieces, etc..

No one even batted an eye and the bag went straight through the carry on x-ray machine. This was in San Jose, California while preparing for a cross country flight. I was surprised too.

A year or so back my son and his friends built a muon detector as a high school project, and then flew it from London to Germany and back to measure muon rates at altitude. Basically two metal boxes glued together, with some hand cut holes for display and power. Inside, a large block of solid plastic scintillator, wrapped in foil, with a bunch of hand-made electronics connected to it. Suspicious? Only a bit. I wrote a letter on headed university paper, explaining what it was, and with contact details in case they needed to phone.

At Stansted, the kid carrying it got the third degree, eveything put though the explosives sniffer, and so forth. The security person afterwards told him it ticked all the boxes except one for a bomb. Would love to know what that one was! They did eventually allow it on the plane though, and got really good data from the flight.

On the return flight, security at Cologne didn't look twice - just went straight through the x-ray machine, didn't even get pulled aside. Must have been asleep on the job.

When in university, I took part in a CUBEsat effort.

I brought the mechanical assembly -no electronics, just the aluminium structure- of our satellite to CalPoly for a CUBEsat workshop; on the way back to Europe I found out the hard way that anything which goes into space is considered munitions as far as the US DoD is concerned.

Took a while longer than expected to get on my flight...

The TSA did an internal audit where they sent 70 mock explosives and weapons through checkpoints. 67 made it through.