Touch a liquid surface with a sharp needle and pull it gently – the force you exert is essentially determined by the surface tension of the liquid. This classical capillary phenomenon was revisited in a recent paper, published in Physical Review Letters, when a thin elastic film floats on the liquid surface. The presence of a film increases the force that is needed to poke the interface, as might be expected. Surprisingly, however, it is not the mechanical properties of the film that stiffen the interface, but rather the interplay between surface tension, hydrostatic pressure and the finite size of the sheet. This universal, material-independent response, is attributed to a novel geometrical concept that the authors call “asymptotic isometry”: the film is so thin that it easily forms very fine wrinkles and in so doing eliminates any strain within itself. How then does stiffening of the interface occur? The role of the film becomes solely to transmit the effect of poking to a larger region of the liquid than would be possible with a regular meniscus. Controlled experiments that confirmed this scenario employed ultra-thin polymer films, but the same geometrical principle is expected to govern the mechanics of poking in various other materials, including the thin layer that forms on warm milk or custard.