Final answer:
An orthographic projection is the type of drawing that can show a piping fabrication most clearly on a spool sheet, giving a detailed multidimensional perspective necessary for fabrication.
Step-by-step explanation:
The type of drawing on the spool sheet that can show a piping fabrication most clearly is an orthographic projection. This type of drawing provides a detailed view of each section of the pipe system. Using multiple views - top, front, and side - orthographic drawings allow fabricators to see the arrangement of the parts in three dimensions, clarifying the spatial relationships and dimensions necessary for fabrication. An isometric drawing may also be used, as it offers a pseudo-3D view which can be helpful for visualizing complex assemblies, but for clarity in fabrication, detailed orthographic views are typically preferred.