Hello everyone. My first post and what lead me to this site. I can not find the original post but it was in regards to why do rat trap carriers have a spring loaded "L" shaped hinge and what good are they.
I am just getting back into cycling after many years. Thousands of miles peddled in the 60's and 70's, most on 10 speeds, all with a rat trap. I always used a cardboard box close to the size of the trap and about 8" high. If you cut a slot in the bottom about where the spring is and another about where the leg of the "L" you can feed the box through them and wind up with a carrying box that won't fall off and carries quite a bit. They last a long time, are easy to make and free.

Here's a thread about just this... Miamijim's answer seems to make sense, but then so do they all.

https://www.bikeforums.net/showthread...rap-rack-thing.

They're good for covering up all the other rattles, squeaks, and noises on a bike.