No Foot Rise means you leave your heel on the ground even as you rise in the body - and often as your partner is rising in both body and feet. Two primary places it is found:
On the first step of the inside of turns - you stay lower in the foot, with the eventaul rise as you leave it taken from the knee
In backwards actions where you are expected to roll through the foot - you can rise in the body, but you must keep the heel down if you are going to be able to roll your weight off the back of it. The lady has this most of the time in foxtrot, but it shows up for both partners in many dances.