I've had a little play around here with the traditional square with castors attached to the bottom and have come up with a major breakthrough - the rectangle with castors attached to the bottom.
This may not seem like a major leap forward but neither did the loincloth - and you need only go to the local mall to see the shopping orgy this created.
The reason I've gone with a rectangle is to make it easier to get the heavy object on to the trolley. The wheels are still set out in the traditional square format but the ledge created by having a rectangular base means you're able to lever the pot on to the trolley, rather than struggling to lift it on. Using castors with brakes also helps, as it can be a struggle to get a heavy object on a trolley when it's moving all over the place.
Step 1
Cut a rectangle from 20mm ply. I've used leftover 12mm ply, one board being 400x400mm and the other being 400x600mm, ideally both sections would be 400x600mm.
Step 2
If you are using 12mm ply, glue the two pieces together and screw to hold in place.
Step 3
On the back, mark out the position of each castor and the bolts. If you are using castors with brakes, make sure the brake is accessible to your foot without the ledge getting in the way.
Step 4
At each bolt position, drill a 2mm pilot hole right through the plywood.
Step 5
Turn the plywood over and drill shallow holes to countersink the bolt head into the ply, approximately 5mm deep. If you use bolts with a dome head this step may not be necessary.
Step 6
Drill the remaining bolt hole through the 2mm pilot hole. This hole will be at the diameter of the bolt you are using.
Step 7
Thread the bolts through and attach the wheels using a socket.
Step 8
Using a file or sander shape the edge of the trolley so it sits neatly on the ground when the trolley is tilted. Tidy any excess glue or rough edges.