Sounds like my steps - the triangle slides in up top first then drops into a hole in the bottom and just hangs there.
The holes in the back is where I stick the pucks in - you may want to do that just to keep algae at bay - my first year went well without it, but in the second year, i was continually getting algae just past the steps (direction of flow), and I finally looked inside and it was greener than green in there - threw a couple of pucks in and stuck the hose in 3 days later to get rid of the dead stuff - problem gone.

By the way, ever time someone uses the stairs, your Chlorine will disperse out of the stairs some - especially when the kids are jumping and goofing off from teh steps.