Thread: what is this part and what is it supposed to sit like?

Its the little thin bar spring thing that hooks onto the two bolts. Has a little u bend in the middle. I ask because it fell out when I pulled the filter and I don't know if it should be loose or tight. What does this do? Is it an electrical switch or pressure switch or something?

I see a picture of the part in those photos, but I didn't read anything about what it does, or how it should sit. Feel free to point it out if I messed it though.

Is it just supposed to hang loose or be tight?