Analogical models are common in scientific and technical literature but scientific/technical communicators may be reluctant to write clarifying comparisons for fear of producing inaccurate or inappropriate similes. Technical writers can use the logical operations that underlie all metaphorical thinking consciously as prewriting strategies: they can learn to construct their comparisons using the logical operations of identification, distinction, re-classification, and division. Applying these logical operations to the generation of useful analogies can give writers confidence that their comparisons possess the qualities of specificity, clarify, richness, scope, and validity.