Idea to made them appear if you exchange floor system. Assumptions was to create them simple and cheap, both are passed. Material is pine wood and PCV pipe, reinforce by thread rod and fill by sand ( better weight). All screw together and glue that's make construction stabile. Only one shortcoming are rubber legs. I didn't want to buy spikes becouse it would make construction expensive, I'm thinking about made some by myself. Wood is stain and finish by mat lacquer, pipe is black mat paint. Connection pipe - wood is seal by silicone, to avoid loosing sand. Sand is dry and clear sand from sandpit so I believe nothing is going to came out from it
All costs are about 55$