I often want kruler to be on top of all the other windows I need to measure on my desktop, but there is no option to set the ruler to stay on top of all other windows. AFAIR in KDE3 this was possible. Reproducible: Always
Workaround: minimize it into the task bar, then set it as "Keep above others" through the context menu of the task bar.
*** This bug has been marked as a duplicate of bug 317436 ***