Re: How do you know you have the right line for your rod?
Since many here are gear and casting freaks I find it suprising many don't have the Umpqua scale.
It can be tweaked and calibrated bit using a known weight which is great since most all doubt about its accuracy can be removed. To further eliminate doubt you can always do a comparitive measurement at the weight the line is supposed to be.
I keep a small slip of paper in the alligator jaw to place 30' of line in large loops in the paper. the tag end of the line adds weight so always make sure to minimize it's influence somehow. I usually just hold it next to the loops so as not to add weight.
The Umpqua scale is a handy contraption that is always in my reel case. I use it quite a bit for friends and fellow club members who aren't sure of their line weights.
The 30' standard may not be perfect for all lines and situations but for the everyday fly fisher who just wants an idea of what their true line weight is it's a pretty handy device.