instrumental — serving as an instrument or means in pursuing an aim or policy

a skilled carpenter holds a hammer and carefully positions a nail against a wooden beam. He strikes the nail precisely to secure two pieces of wood together permanently. Without the hammer as his tool, he could never join the wooden pieces effectively. The hammer serves as the key instrument that makes his construction work possible. Other workers nearby use different tools like saws and drills for their specific tasks. Each tool becomes instrumental in completing different parts of the house construction. tools serving as instruments or means in pursuing the aim of building