Does anyone know how I could narrate if the nouns belt is slipping on a small commercial mower? The instruction manual says to check it once a year and to...

The instruction manual says to check it once a year and to tighten or replace it.

how is a simple track to tell if the transmission belt is slipping or not.

dont want to lavish my time with meaningless things, but I dont want to damage my mower any.

Thanks for your answers!