Forming tools are parts that act as dies that bend, stretch, or otherwise form sheet metal to create form features such as louvers, lances, flanges, and ribs.
The SOLIDWORKS software includes some sample forming tool parts to get you started. They are stored in:
<install_dir>\ProgramData\SOLIDWORKS\SOLIDWORKS <version>\design library\forming tools. You can add this folder to the Design Library by setting it up in File Locations.
You can insert forming tools only from the Design Library and you can apply them only to sheet metal parts. A sheet metal part has the Sheet-Metal1 
feature in the FeatureManager design tree. The part on which you insert the forming tool is called the target part. You can create your own forming tools using many of the same steps you use to create any SOLIDWORKS part.
Before you apply forming tools to sheet metal parts, in the Design Library you must right-click the folder that contains the forming tools and select Forming Tools Folder to designate its contents as forming tools. This applies to forming tools that are part files (*.sldprt), not Form Tool (*.sldftp) files.