Somewhere I read that it is not customary to reward workers on site with extra cash so I haven't done this so far. But when the solar panels were installed on top of the roof it was really hot - 35*C in the shade - so I thought I will give the people some money that they may buy some cold drinks. They looked at me as if I came from Mars. When they left the premises one guy came back and put the money underneath the doormat. An embarrassing situation.