Use a real body location and a rough physical description. “Inner forearm, about 15 cm tall and 10 cm wide” is more useful than “medium.” If the concept should cover a region rather than fit a rectangle, say that: half forearm, upper-arm panel, outer calf, or wrapping from one landmark to another. The forearm tattoo guide shows how eight reviewed works use that placement across four styles. For full-arm coverage, the sleeve and half-sleeve guide separates complete-arm views from large components and explains hierarchy, transitions, stopping points, and estimate boundaries. For hands and fingers, the hand and finger tattoo guide separates exact surface, coverage, visibility, and longevity claims.
Approximate is enough for the first message. Final measurements and the stencil happen in person. A clear photo of the placement can help show the usable area, existing tattoos, scars, curvature, or where you want the composition to begin and end. Do not edit a design onto the photo; the purpose is to show the body area.