You can modify the sketch by changing any dimensions that are visible; however, when you are modifying linear and angular dimensions, you must indicate which vertices will be affected by the change. Only vertices that can be moved unambiguously are valid choices. For example, consider the sketch shown in Figure 19–10. If you choose to modify the dimension, you must decide whether that modification will affect vertex 1 or vertex 2. If you select vertex 1 to move, vertex 2 will remain fixed when the modification is made, as shown in Figure 19–11. The reverse is also true; if you select vertex 2 to move, vertex 1 will remain fixed, as shown in Figure 19–12. You can select multiple vertices to move when modifying a sketch. However, selecting both vertex 1 and 2 to move would be an invalid choice in this example, since it would not be clear which direction the two vertices should move; ABAQUS/CAE issues an error message in this case. You could select both vertex 1 and 3 to move; the resulting sketch is shown in Figure 19–13.