As Doug Demaw, W1FB, prothesized back in 1976 with the introduction of the Tuna Tin 2 project, food cans make great chassis for QRP projects. While you get them free with many of the foods you already buy, buying an item just for the can is also quite cheap...
Look for cans with easy open pull tab lids as after you remove the lid, a small shoulder is left around the top to set the project board on. A clearance hole in the center of the can bottom for a #6 bolt or threaded rod for taller cans used to hold the board in place is all that is needed to modify the can for use as a chassis when building a project using one of QRPme's can prototyping boards. Food cans come in a limited number of sizes.
QRPme proto boards are industry sized for 211, 300, 307 & 401 cans:
211 which are 2 11/16" diameter primarily used for personal or 1 serving cans
300 which are 3 00/16" in diameter primarily used for 14 to 16oz vegetable cans
307 which are 3 07/16" diameter primarily used for tuna, fruits like pineapple etc, and pet food
401 which are 4 01/16" diameter primarily used for family size meats like canned chicken & turkey

The Tuna Project 211 Board (211 can). Build your own tiny tuna can accessory item!.
The Corn Challenge Board (300 can). Build a unique gizmo in a 'standard' veggie can!
The Tuna Project Board (307 can). Build your own tuna can accessory item!.
The Tuna Manhattan Construction Board (307 can). Build your own tuna project Manhattan style!
The Tuna Project Board 401 (401 can). Build a bigger project in a bigger can....