Temporary structures are often built using scaffolding systems – in these cases, the scaffolding system acts as an architectural expression of transition. From a structural point of view, stiffening the resulting square grids with diagonal rods is an exciting task. The aim is to create a rigid, structurally sound structure with as few elements as possible. Grid bracing is one of the most-researched areas of structural topology [1,2] . During the TDK, we deal with the spatial extension of a variation of the plane  task: the aim is to create a small grid, say 4*4*4, with an ’empty’, say 2*2*2 cubic space inside. Elementar approaches (including  modelling) acn be effectively used, but it is an advantage if it is chosen by a student interested in linear algebra and graph theory.