The guy knows his nails, and how to avoid getting screwed. A contractor asks for a substantial down payment on a job for any number of reasons. A contractor arrives at a job and works hard producing lots of activity. He asks for a payment and the customer gladly yields.
More work happens and more money is handed over.
About this time the contractor pulls the famous disappearing act. Installing screws is way too labor intensive. Nails work just fine for 95 percent of the tasks. Say I want to be my own general contractor and hire subcontractors to build my house. The first mistake will be assuming that the subs know exactly what to do when they show up.