1a. Grasp your knife use above image to get it right .when cutting on the floor, your thumb has the power to add the nessasary force to move the knife. and importantly, a brake

1b The most common error is too much pull on the knife – it slips and cuts further than you intended. Your arm arm has too much power to be let loose on such a small area. Use it in combinaton with your thumb. Let Your Thumb do the work