Marking out the strike plate
With the new latch fitted, close the door against the frame with the latch protruding so that it touches it.
Mark the top and bottom where it touches and open the door again.
Transfer these lines horizontally on the frame rebate.
Measure the distance from the closing edge of the door to the far edge of the latch.
Mark this distance from the door stop on the frame rebate.
Hold the strike plate in position on the frame so that the far edge of the cut out lines up with the mark just made and the horizontal lines match up with the top and bottom of the cutout.
Fitting the strike plate
Mark around the strike plate and recess the frame to suit.
Check that it fits neatly before drilling pilot holes for the screws, and fixing in place. You may need to countersink the wood to accomodate any shaping on the back of the plate for the fixing screws.
Check the operation of the latch when the door closes to ensure all items are lined up properly.
Slight adjustment in any direction may be made by slackening the strike plate screws and moving the plate. Holding it firmly in its revised position, re-fasten the screws.