lay a foundation

Figurative senses from the idea of laying a foundation as the first step in constructing a building.

lay a foundation (third-person singular simple present lays a foundation, present participle laying a foundation, simple past and past participle laid a foundation)

1. (law) To elicit information from a witness to show that the witness has knowledge of a matter before the witness testifies to the matter itself.

   In order to lay a foundation for the witness to describe the murder, the prosecutor first had to show that the witness was present when the murder occurred.

2. (figuratively) To make a start.

   You should lay a foundation, even if you can't finish the project.