Tip the Cabinet Installer?

We’re having kitchen cabinets installed by a local, privately-owned company. They contracted out with a local woodworker to put them in. He’s spent two days here, and they look great – he really seems to know what he’s doing, and is doing a good job.

Is it customary to tip for this? I mean, we paid for the cabs and install and all…I would expect that he do a good job for such an expense.

Do I tip the cabinet guy? If so, how much?