/diy/ - Do It Yourself

What I'm missing here?

>installed capricorn tube time ago, top part of coupler didnt fit in place, I supposed it be like that since originally was like that.
>noticed is not supposed to be like that.
>tube is literally destrolled now, had to cut it.
>teeth were pointing up. I dont know how is supossed to be.
>If insert teeth pointing down the top part fits but is loose, and tube is loose.
>dont know if there is a missing piece or what