Rebar dowels set along the footing before the pour, Newmarket, ON.
Sized to the load
Wire mesh, rebar, or both — matched to what sits on top
A shed pad and a garage floor rated for a loaded pickup don't need the same reinforcement, and pouring them the same way is how you end up paying for more steel than you need, or not enough. We size thickness and reinforcement to what the slab is actually going to carry.
Where a slab ties into an existing footing or foundation, we set dowels so the new pour is structurally tied in rather than just butted against it.