Step 3: The Cover
You'll need to attach the cover, if it isn't already attached. Using a record you do not want, secure it to the mounting bracket. Close the cover and mark it's location. Cut a slot across the cover and test to make sure the record fits without touching when you close the box (think Buster Keeton and you'll get it right:-).
Now, take the entire kababble outside and hook it up to your garden hose. You can see I've added a 90 degree bend to the inlet side and am using the washer hose. With my sink setup, this is what will work best, and I want to test everything before I mess my tools up again.
Lots of spray will come out of the slot, but we're going to open the top anyway. Don't turn the water up too high or you'll be sorry. Adjust the spray heads so the spray just covers the 4" where the grooves of the record are. Slowly turn the pressure up and check if your brackets are strong enough to keep the spray on target. No pics... My camera wasn't going anywhere near that shower.
When you're satisfied, undo the water connection, empty any water our, dry the top off and take it back inside.