The two pictures below show the 1.75" flat trim being applied. The picture on the left shows the trim being used to finish the interior after a vinyl retrofit window has been installed. In areas of the country where retrofit frames are not available, a standard block replacement style frame can be used, then the flat trim can be applied to the exterior as well as the interior as shown in the picture on the right. The back of the trim now has deeper grooves to enable the installer to reduce the width with less effort. 2 1/4" trim can be reduced to 2", while 1 3/4" trim can be reduced to 1 1/2", 1 1/4", or 1".

If the wood that you need to cover is 3 sided rather than just two, then you need to use a combination of angle pieces on the ends and the flat trim in the middle. In the picture below, 2 1/4" flat trim was applied to the front, then angle trim was added on the ends.