First reading is getting the length right #1. Here is #2. Only one chalk mark is placed to mark the length. I prefer to place it on the right front crease. A ruler is placed on end on the floor and against the back of the right leg. A chalk mark is made at the top of the ruler and on one leg, then on the other leg. On the work table, lay the trouser flat on its right side pocket and side seam. The left leg then lies evenly on top of the right. Flip the lower part of the leg back on itself enough to give you space to work on the right side. Now that right front crease should lie on the table and facing you. You should see the length chalk mark now. Place your ruler on the length mark and have the ruler lie squarely across the inseam. Now pivot on the length mark and lower the ruler at the back crease about a half inch. Thats the angle of your plain hem. Now chalk a line there.Transfer the two ends of the line to the other side of the leg, and chalk a line between. Now lay the two legs down together left on top as before. The two creases together as well as the two inseams. Now check the chalk marks on the back of the legs. If they are together the legs are even. If they are apart lets say left is higher , that means the left is lower. Now slide the left leg down to make marks even. Now transfer the hem lines to the left leg This is when you allow for the hem to turn inside, and then cut off the excess cloth. The process is the same for cuffs.