The credit for this tip goes to my husband. He noticed workers in used furniture stores using these to move large items. I'm the benefit of his experiment; I've been singlehandedly moving chests and mattresses all morning. This type of flat dolly doesn't require the arm strength required to tip and push a two-wheeled version. My husband made it in less than fifteen minutes with scrap materials. It's simply two-by-fours cut and screwed together, with a set of cast-off castors screwed to the base. We stapled an old carpet remnant around the top for padding. Even if you bought the materials new, I doubt it would cost less than $10 to put together.
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Update: Thanks for your questions. The critical thing is not to make your furniture dolly too big to fit through a doorway! My husband says to take an 8-foot 2 x 4 (cost, about $2) and cut it into four 2-foot sections. The finished dolly will be 2 feet by two feet. Scavenge the casters if you can, as they are the most expensive part of the project. As for getting the furniture ON the dolly by yourself: I lifted one end of the chest and then pushed the dolly underneath it with my foot. Then I lowered my end back down and pushed the whole thing along. For larger pieces (like the roll top desk), I maneuvered the dolly underneath one end and then lifted the opposite end as I pushed. This makes the dolly work like a second person on the other end.