An assembly saves time. You measure one quantity, and the assembly expands it into every part and the labor to install them.
Example: a drywall estimator builds an assembly for one wall type. It holds studs, track, board on both sides, screws, tape and finish. The estimator measures linear feet of that wall, and the assembly produces each quantity.
Build assemblies from the wall type legend and the spec, not from memory. Check each new job for differences such as stud gauge or board type. A wrong assembly repeats its error on every foot you measure.