cutting angle

[whyme!]

I have a plate 4x2 bolted to a wall and i want to fix a rafter from that to a wall plate on outside wall.
If i rest a 4x2 ontop of the plate bolted to wall and the other end to outside wall.
Will it work if i draw a line vertical(plumb) from the wall plate (bolted to wall) then one the other end vertical(plum) from brickwork.

Cut these then on the outside wall end mark a line at 90 degrees for birdsmouth

 

[Harbourwoodwork]

Ineffect you are scribing the rafter in and this method can be used only if the top and the bottom of the rafter drop by the same amount,to make this easier do the plumb cut at the top, position this against the top wall plate,but position it high by the same amount the bottom has to drop to make the seat cut.If that is a bit complex send dimensions :wall plate outer edge to other wall, thickness ridge board,height to top of ridge board from top of wall plate?

 

[whyme!]

So basically do as i intended, only first cut the edge for the plate bolted to wall first.
Offer up and raise it say 3/4 inch on that plate then mark other end as described in post one. cut and then when it drops down that 3/4 inch it should be snug both ends?

Or do you mean offer up first with it say 3/4 inch high, then mark both ends in this position then cut?

Would this not be the same as doing as i first intended with rafter sitting on plates butted to wall, mark but then take an extra 3/4 inch off the plum on the top?

I assume if i cut the top as i inteded first, when in position it pushes the other end out by 4 inches if on a 4x2 plate? ( 4 inch drop from scribed position)

 

[Harbourwoodwork]

Offer rafter to the face of the ridge board,but push the rafter up the the distance to the seat cut to top of wall plate so it all drops vertically into place

 

[whyme!]

Thanks
I found this and together with your help, i seem to understand now
http://www.builderbill-diy-help.com/rafter-length.html