Exactly six gear-shaped amphiphiles self-assemble into a highly stable, water-soluble, box-shaped capsule, in which indented hydrophobic surfaces of the components mesh with each other like gears. A water-soluble, tetrahedron-shaped capsule was also constructed from four gear-shaped amphiphiles with a template guest. These findings provide a guideline for creating aggregates with a given number of amphiphiles based on hydrophobic surface engineering.