падать уровен. Спусться уровен или шаг.
A 'wrung' is a step on a ladder. A 1.8m ladder might have 5 steps or 5 wrungs. So if you drop a wrung, you come down a level, you come down one step.
You can use this phrase figuratively too, as a figure of speech. E.g. When the girl said 'no', the boy's self-esteem dropped a wrung. )))