I used some scrap wood to make corners for the cages. I cut them on a 45 degree angle so they did not hobble me as I walked around my garden. I screwed in 4 castors - two that swivel and two that do not (because they were cheaper).



The castors I used are a little small for the weight of the garden, I would recommend assuming the soil will weight the same as water (1 cubic centimeter of water = 1 mL = 1 gram).



To get the weight, measure the volume (length x width x height) of the soil in cm and divide it by 1000 to get the weight in kilograms AND the volume in Litres. Soil and compost are sold in litres so this is a handy number to have. Don't forget to divide this weight by the number of wheels to get the weight on each wheel.



If you are in an Imperial country, measure the volume in inches (length x width x height) and multiply by 0.03606 to give you the weight in pounds (lb). As to the volume - I'm sorry, I'm an engineer and even I find it confusing to use inches, pounds and gallons!

