Sure you may be a great inventor, but you are not a mastermind at everything. At some point in your process of inventing something, you may get to the place where you need help having a part or parts made. These are usually called prototypes. Prototypes are parts that basically are first production sets. They may be a bit crude looking but essentially will still fit into place and do the job for testing purposes.

You may need a plastics extrusion facility to do some work, or perhaps a sheet metal shop to press something out for you. Either way, this may be a necessary part of your invention. Keep in mind that sometimes it is hard for you to do everything yourself.