Where do I deduct lumber siding roofing materials and other materials I used for building a garage for a customer

[Hal_Al]

You can enter it as "Supplies" (line 22 of schedule C).  Alternatively, you can enter as "other expenses".  This will allow you to enter a label, such as "materials for Johnson garage job".  It will be listed in part V of schedule C and the total of all other expenses (all you job materials) goes on line 27a of Schedule C.