The Hem tool creates a hem allowance on your patterns. The program will measure the width of the item at the fold distance and adjust the final hem line/curve to match. If you have a pattern that flares out or in at the hemline, this tool will makes sure your hem is as wide as it needs to be when folded to the inside.

For this tool to work, you must have a line/curve drawn at the edge that will receive the hem. You also need lines/curves connected to this on both sides. In the images below the hem edge is the bottom of the pants and the sides are the inseam and outseam lines.

Select the line on the pattern edge that will receive the hem.

Next, select the side lines that are connected to the hem edge line.

Enter a value for the Hem Depth. This is how much of the fabric you will turn under to form the hem.

If you need to finish the pattern edge with a turn over before hemming, enter a value for the Raw Edge Turn. Note that you will not see the results of this value at this point. It has been added to the new hem line as a Seam Allowance value. 

This will create a new line at the depth of the hem. The original line will be changed to a Fold Out dashed line for your reference.

You will need to use the Add Line tool to connect the new hem edge with the side lines.

Once you have applied a Seam Allowance to the pattern, the Raw Edge Turn  value will be seen. In the following image, the seam allowance around the pattern is set to 12mm / 1/2", but you'll notice that the hem edge is only 6mm / 1/4", as defined during the hem process.