The Earth's magnetosphere is an accessible region for improving our knowledge of the dynamics of collisionless plasmas. We focus here on the magnetopause a typical plasma discontinuity. We discuss recent developments in describing the structure of the magnetopause by means of reconstruction techniques, which translate in situ data into spatial information. We review short- and long-duration reconstruction methods and discuss the ideas behind them. The emphasis is on long-duration reconstruction methods in a multi-spacecraft context.