A method of preparing a two-dimensional sheet of material for bending along a bend line to form a three-dimensional article having a fluid-resistant bend includes the steps of forming at least one bend-controlling displacement in the thickness direction of the sheet of material, a portion of a periphery of the bend-controlling displacement proximate the bend line defining a sheared face directed toward an opposed sheet surface in the sheet of material on an opposite side of the bend line, and bending the sheet of material. A balancing of the forces during bending produces face-to-surface engagement between the sheared face and the opposed sheet surface such that the sheet material is substantially fluid-resistant along the bend line.