Hipped roof:
If the roof does not have a gable end. Begin your first sheet where the angle of the top ridge drops down laying your longest sheets first across the top ridge. When you finish the last sheet coming across the top ridge board and are beginning to drop down into the lower hip stop and measure the triangle of the roof sheets now still left to do on this side. If there is a large enough area of ground to lay out these same size sheets already with laps and taking the measurement of the widest bottom by the spouting end of this triangle of cuts to be made. Mark this measurement of the very corner on the sheets laid out on the ground. Then place the measurement of the distance the right-angled side of the triangle rises up the sheets to the top of the triangle from the spouting edge of the sheets. Run a chalk line between these two points and flick on the chalk. Double check your measurements by choosing a measurement in from the sheets already laid say 6-feet (1.8 M) in and measure how long the section of roof is at this point on the ridge from the point 2-inches (50 mm) into the spouting. Check you have the same measurement on your chalk line. If so you have the correct angle and you are all set to cut this chalk line off with either a pair of straight tinsnips or an electric steel nibbler.
Then simply run out your insulation building paper and place your first longest sheet lapped onto the sheets you have already laid. Then at the spouting end sit the sheet where it is 2- inches (50 mm) into the spouting and double check the other side to see that it is also 2- inches (50 mm) into the spouting. If it is not you may have to at times shrink the outer edge of this sheet to assist it to come around to square on again. To shrink the side of the sheet. Place fixings in the lap joint and then lift the edge of the sheet in the middle to shift the outer most edge back shrinking it towards the lap side of the sheet. Now with the sheet puckered up in the middle place a fixing on the outer edge opposite where you want the sheet to shrink either at the top or the bottom. Then place the rest of the fixings in after rechecking your 2-inches (50 mm) into the spouting mark against the timber or steel fascia board.
If the pitch of the roof is lower enough to easily walk all over you can flick chalk lines after pinning the entire roof on the laps and place the final fixings. However if the roof is very steep and you are constantly working off the purlins fix the sheet off fully as you go with short flicks with your chalk line.
Note: The off cuts from the first triangle you cut will go on the opposite hip section of the roof. When laying these, start with the first two small sheets and line them up into the spouting off the edge of the fascia board using your 2-inch (50 mm) in marks.