Sometimes misspelled as FASTATCH, there are the build-your-own potentiometer using one or more parts which include:

• Front control
• Rear control
• Single Tap control
• Dual Tap control
• SPST or SPDT switch
• Shaft - single or dual shaft, cut to length
• See PDF for chart of various tapers and types of controls that may be available

These were designed to replace controls from most equipment made during the 1940s through the 1980s and later...