Rudder rake is the VERTICAL aspect of the rudder with respect to the hull. if you
look at the boat from the side (ie up on the trailer). The leading edge of the rudder should be slightly forward of the gudgeon. It should be enough so that you have the same feel that xanderwess described before- there should be some rake. Less rake increases drag and slows the boat, more rake decreases drag, BUT it can make the boat behave sloppily when trying to maintain a steady course.
"Toe in" is a fish of a different color. The shop is correct: there should be NO toe in. The rudders should be exactly parrallel to each other operating in the same plane, if not, you either have toe-in or toe out. To get your rudders parrallel: looking at the rudder from the side, draw a pencil line from leading edge to trailing edge AT THE WIDEST POINT of rudder. Draw the same line-
in exactly the same place- on the other rudder. NOW viewing the boat from the rear, measure the distance from trailing edge to trailing edge using the line you just drew as a reference, then measure the distance from leading edge to leading edge on that same line. You should have exactly the same distance from trailing edge to trailing edge as you do from leading edge to leading edge. If not, you have to adjust the tiller connector bar to one tiller or the other, depending on which side you have your tiller bar adjustment ge-gawk, until those measurements are equal.
Now your rudders both cut through the water parrallel to each other faster and cleaner. Leaner and meaner. Cool
mmiller is correct in a way- if you sail mostly with one hull up and one down, you may have better tracking if you are toed- in a little. But if you sail mostly flat- keep 'em parrallel
Come sail away, come sail away, come sail away with me lads (I hate that song
)