Signage for use on a substrate having a porous surface, the signage being substantially visually indistinguishable from the substrate to an ordinary observer when the substrate is dry but readily visible when the substrate is wet. The etchant and polymer precursor species contain fluorine, and the chamber ceiling semiconductor material includes a fluorine scavenger precursor material. The cap is rotatable between a first position in which the cap at least one recess aligns with the tool at least one recess, and a second position in which the cap at least one recess is out of alignment with the tool at least one recess. The models can be used in structure-based drug design studies to identify drugs that bind to particular structural variants in structure-based drug design studies, for designing allele-specific drugs, population-specific drugs and for predicting clinical responses in patients. The coded data is disposed in accordance with each sub-layout including rotation-indicating data that distinguishes the rotation of that sub-layout from the rotation of at least one other sub-layout within the layout. This decreases, within binary data from a data bus, the number of bits that change from 1 to 0 or from 0 to 1, further decreasing electric power consumption and enhancing a communications speed.