What it means
A jack of all trades is someone who's handy at loads of different things and can usually muddle through whatever job lands in front of them. It can be proper praise for being useful and adaptable, or a cheeky dig if they're forever dabbling and never quite mastering any one lane. People often tack on master of none when they want to add a little sting.
Usage examples
"Gaz sorted the leaky loo, bodged that dodgy socket, then knocked up a wonky pallet shed. Proper jack of all trades. Master of none, mind, but it’ll do."
"He fixes cars, bakes bread and plays guitar, a proper jack of all trades."
"Ask Priya, she can patch drywall, sort your Wi-Fi, then bake a birthday cake by six. Absolute jack of all trades."
"My uncle's a proper jack of all trades. Bit of plumbing, bit of electrics, bit of carpentry, somehow the house is still standing."
"Maya's basically the office jack of all trades. She'll sort the printer, patch the website, then somehow rescue the coffee machine too."
Where it comes from
It goes back to the old English word jack meaning an ordinary man or worker, not one specific bloke. By the early 1600s, jack of all trades was already used for someone who could turn their hand to loads of jobs. Master of none came later as the sharper little sting.