Thanks for the advice! I sorted my key and then used VLookup with the switches, and it works now (not that I really understand how it works, but that's okay).
All spreadsheets, from the very first one
http://www.danbricklin.com/history/vcexecutable.htm, are designed to lookup exactly the other way round. They use to lookup a distinct category from a
scale of numbers.
In your original document, sort E1:F14 by the numbers in F, then put some numeric search values in A, a negative, a big one (1000) and some fractions such as 3.4 and 1.9 . Then use
B1 =LOOKUP(A1;$F$1:$F$14;$E$1:$E$14)
LOOKUP is designed to match at the last position on an ascending scale where the search value is greater or equal, so you get results for all possible search values except the negative ones where the search value is already smaller than the first possible match.
By default MATCH, VLOOKUP and HLOOKUP match in the exact same way, but they provide an additional switch to lookup exact values in unordered lists rather than categories in ordered scales.
MATCH_0_1.ods demonstrates both methods (and btw another glitch when matching strings without knowing the pitfalls).