0 a long, narrow device for calculating numbers with a middle part that slides backwards and forwards -- regla de cálculo
1 an instrument for calculating, like a ruler in shape and having a central section that slides up and down between the outer sections. -- regla de cálculo
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.
Podemos completarlo paso a paso, por muy largo que sea el camino, y no se puede completar, por corto que sea el camino, si ni siquiera marcas tu huella.