Oh for pete's sake!! Here's where it gets confusing.... Page 6 of the tournament rules under Measuring:
A player cannot use multiple rulers or maneuver tools to measure additional range, distance, or movement beyond the length of a single tool or to triangulate measurements.
So, can I use ONE ruler and ONE maneuver tool? Note it says "multiple rulers OR maneuver tools"....
As for the underlined part, okay, so I am restricted to measuring movement just using one maneuver tool, that's fine. But the question here was about using ONE ruler and ONE maneuver tool.
Note that one item is called the RANGE RULER and one item is called the MANEUVER TOOL. In a game where terms such as "at, within, beyond" and other words are defined, calling a ruler and a tool collectively as a "tool" just doesn't sound right.
Now refer to Page 9 of the RRG under Premeasuring:
Players can measure with either side of the range ruler at any time.
So, can I put down the maneuver tool beside my ship (but not slotting it in), then use the range ruler to make sure that I am not going to be in range of my enemy's ship at the start of the next turn?
Those were the questions that I was personally asking (and what I was reading as confusing to others as well) and Gibbobobo's reply from FFG seems to have cleared this up.