How high is a knee?

I’m translating a leaflet for a tennis club (variety is the spice of life!). They use a tally system for booking in guests, in Dutch ‘turven’.
Searching for the best translation for the word ‘turven’, I came across the expression ‘drie turven hoog’ (three turven high) with two completely different translations. One was ‘knee-high to a grasshopper’ (correct, and such a lovely expression!) and the other, ‘elephant-like’! Procrastination! Now I have to look up the origins of the words turven and tally. There will be links and historical facts and I will spend at least half an hour surfing and reading (and writing this blog) before forcing myself to get back to work!
So a turf is a flat square of peat, dried and used as fuel (not advisable – it emits more CO2 than coal!). Three such squares stacked will not be very high. In German, they say ‘three cheeses high’.
The only use of ‘turf’ as a verb in English is a slang way of saying ‘throw something or someone out’: they were turfed out of their house.
And what about ‘tally’? Historically a piece of wood, with notches for the items of an account, split into two halves, with each party keeping one half. In bookkeeping, the columns should tally, or correspond. And of course, to keep score.
Back to work!