Next, we will apply fixed boundary conditions to the four nodes at the base of the model.
Click View Navigate Orientation Front View.
With the Selection Shape Point or Rectangle and Selection Select Vertices commands active, click and drag to draw a box enclosing the bottom of the model as shown in the following image.
Click Setup Constraints General Constraint. Notice that the text in the title bar of the dialog box:
"Creating 8 Nodal General Constraint Objects"
The reason for this is because there are two coincident vertices at each corner of the base, one for each part.