"Foot in the door" is an idiomatic expression for a strategy to gain a small initial commitment or entry point to build a larger relationship or agreement later on. This strategy is also known as "toehold," "entry point," "initial contact," or "small win." These synonyms suggest the idea of making a small but significant step to establish trust, gain access, or create a favorable impression that can lead to more significant opportunities. The metaphor of "foot in the door" is commonly used in marketing, politics, sales, and relationship-building contexts, emphasizing the importance of starting with a positive first impression and building rapport over time.