How to combine shapes to create a custom shape

There are two ways to create a custom shape:

• Make one shape from some existing shapes,
• Modify an existing shape.

To make a shape from some existing shapes, do the following:

   1.   Add shapes to the slide, for example:

When you select all shapes, PowerPoint shows the Shape Format tab:

   2.   On the Shape Format tab, in the Insert Shapes group, when you choose the Merge Shapes dropdown list, you will find the following operations:

• Union shapes:
  • Combines all overlapping and non-overlapping areas of shapes
  • Subtracts nothing
  • Retains formatting of the first selected shape

• Combine shapes:
  • Combines non-overlapping areas of shapes
  • Subtracts overlapping areas of shapes
  • If selected shapes do not overlap, acts like a group with no option to ungroup
  • Retains formatting of the first selected shape

• Fragment shapes:
  • Creates new shapes from the overlapping area of shapes
  • Creates new shapes from in-between empty areas
  • Retains as shapes any areas that do not overlap
  • Subtracts nothing
  • Retains formatting of the first selected shape

• Intersect shapes:
  • Creates shape from the overlapping area from all shapes
  • If any shapes do not overlap, nothing will be created
  • Removes non-overlapping areas of shapes
  • Retains formatting of the first selected shape

• Subtract shapes:
  • Retains the first selected shape
  • Subtracts overlapping areas of other shapes from the first selected shape
  • Removes all non-overlapping areas
  • Retains formatting of the first selected shape

See also this tip in French: Comment combiner des formes pour créer une forme personnalisée.