A Weak Layer boundary allows you to define a polyline boundary with strength properties, which can be used to model joints or interfaces (for example) along which sliding might occur.
To add a Weak Layer boundary to your model:
Select Add Weak Layer from the toolbar or the Boundaries menu.
Enter the vertices of the boundary as described in Entering Coordinates.
When all vertices are entered, right-click and select Done, or press Enter with nothing in the prompt line.
A dialog will appear which allows you to assign material properties to the weak layer. Select a property and select OK.
NOTE: a Weak Layer boundary is an independent modeling entity and is not considered part of the model boundary geometry. It does NOT get intersected with other boundary types, and cannot be used to define material regions. It is only used for the specific purpose of defining a boundary which has strength properties.