Know and demonstrate your skills (Skills Lesson 1)

From the point of view of the employer, a person is needed to do a job based on a definite skill set.
Example:
S is sent a helper in the workshop. S sets him to work: Can you solder those wires for me? The helper frowns I only do front of house and design of shows. I don't do soldering. S (sighs) Okay - you can clean out the storeroom then.
Later, S to the roster manager: That was another one for the storeroom! Do you have anyone with the skills we need? They're no use to me unless they can do the job. Otherwise I have to spend my time checking the work, and maybe re-doing it...
The attitude of 'Can Do!' is fine if you're not just bluffing about your knowledge and abilities.