A number pattern convention can be used to identify modules when they are brought together to form a cell. In the Image below, Figure A shows a 3-dimensional cube with the faces that are showing numbered 1, 2, and 3 in a counter-clockwise direction about their common corner. Figure B shows the cube unfolded to indicate how all the faces of the cube are numbered in relation to each other. The numbering convention for determining which faces have values 4, 5, and 6 is to arrange them so that the sum of the values from each pair of opposite faces is equal to 7.