To use the Self-Marking Tape Measure — which contains an ink cartridge — you extend the 16-foot tape until the pointer indicates the desired distance, then press down on the case to leave a mark. According to the maker, one cartridge can make hundreds of marks and is easily replaceable when it runs out. The ink is erasable from nonporous surfaces but permanent on raw wood and drywall. The tape measure costs $25; replacement cartridges cost $5. I-Mark Tools, 802/253-9600,