8) Which defect in timber is caused by the growth of branches?

9) What is the name of the operation needed to enable the head of the screw to fit flush with the surface of a component?

10) What is the indication of the letter ?M? in thread formation M12?

11) What is the thread angle of British standard worth (BSW) thread?

12) How many types of threaded fastening available in ISO inch (unified) thread?