A very simple, cheap, upgrade to my shed today. I've always struggled to build things on little folding tables. Today I paid AU$29 for a door and it makes a fine bench.
It's a hollow door so won't take much weight in the centre. I'm thinking of putting some sort of edge on it to stop things rolling off. I'll keep this next picture as a reminder of what it looked like originally.
The door is a narrow model. It's 2040x720x35mm. (I have no idea how many furlongs that is for you Americans).