Prewash Cycle Defined on Top-Load Washers

The Prewash cycle (may also be called Stain Assist) on mechanical knob washers should be used for removing surface dirt from heavily soiled clothes.

Place your clothing items, along with detergent, in the washer using the Prewash or Stain Assist cycle and run that cycle.  It will fill, agitate for a short time, and then drain. When complete, don't remove the clothes load. Just turn to whatever cycle you would have normally washed that load on and another dose of detergent. Then run that cycle to finish the wash process.