so after being broke with all the new babies, I bought, its time to plan their future. im going to build a rack or really a rack shelf cause i will be using ultratherms instead of flexwatt. it going to hold 4- 42qt. tubs and to keep wiring down, im going to use somthing called an octopus surge protecter, has like 5 mini cords coneceted to the outlet, then im using this to plug into the ranco or johnson. so my question is

I see people sitting there tubs on cds, during the pre-build, is this to determine gap?

also what is a good gap

and how would i create a "stopper" like the Reptile Basic rack, that comes with a little white thing, to stop snakes from pushing out tube.

last but not least, is Ranco better than Johnson, or are they the same, i have a ranco with my other rack, and its fine but just wondering