#4963656
After looking for the answer to this for a while, I figured I would just ask.

It looks like something "catches" the cartridge after Ray inserts the trap in the containment unit. But after watching the video a few times,
I'm convinced that maybe he pushes the button on the handle, ejects the cartridge, and then just closes the door. But I'm not totally sure. The cartridge looks like it's stuck in place.

Is there anything keeping the cartridge in place or pulling the cartridge out of the trap? Is there some mechanism for this inside the containment unit door?
#4963713
The Trap prop strongly believed to be the one from the Containment Unit scene (because it's the one that has a removable cartridge) has a unique feature on its front indicator, a binding head screw:

Image

If I had to hazard a guess, there's a plate hidden from view inside the Trap "air lock" that has a hole drilled through it. When they prepped the shot where the casing is slid out, they unscrewed the binding head screw which was also hidden from view, slipped the Trap cartridge into position, screwed the binding head screw back into place, and then slid the casing back onto the cartridge.
#4963819
It’s believed to be just the spring action of a metal lever buried in hilt of the handle. You can kind of see it in the pic above. It moves back and forward slightly. With a hook action at the bottom inside the base of the handle connecting to the trap. Hidden behind the slide since it sits higher. Rays thumb covers it perfectly and allows him to toggle the latch secretly right in front of your eyes.

For real time applications, the light bar and blinker connected by a quick release plug in the trap sleeve to allow functionality as well as mechanics of trap doors.

But for movie purposes. I’d imagine the lights and motor were housed in the trap slide separately from the red blinker on the back. The hero trap was actually non functional aside from a smoking filament combined with a smoking liquid igniter. There were a total of three different ones if I’m not mistaken. The hero (Zeddemore’s hire scene), semi (containment trap), and special effects (slimers trap scene). And not to mention, foam traps.
#4964799
This is something that I've actually been thinking about for a while since I've been modding my Walmart trap. Is it possible that, given the shape of the front of the trap, if it were an actual piece of working tech, were designed to activate some kind of grasping mechanism that is activated once inserted and is disabled once the sleeve is reinserted? It would be strangely shaped to hold the cartridge and still let it go once it needs to do so, but it's the only thing I can think of, if it was a real thing.

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