A Mock-up is the Best Way to Share Your Vision. Sharing a design, a series of samples, or a rough prototype quickly aligns people. Without it, much of a discussion is spent orienting a group around a concept and addressing basic questions and misunderstandings. Without a mock-up, people are trying to interpret something in the dark by feeling one edge at a time. A mock-up or prototype is worth countless meetings and debates. A mock-up turns the lights on.

Quoted from Scott Belsky