You create construction geometry in the Sketcher to help you position and align the geometry in your sketch; objects that you might need to position include holes, arcs, slots, or gear teeth. The Sketcher allows you to add construction lines and circles to your sketch; in addition, points that you create using the isolated point tool 
are considered construction geometry. Construction lines, circles, and points do not appear in the feature you are creating or modifying.
While you are adding construction geometry and moving the cursor around the sketch, ABAQUS/CAE displays preselection symbols at the following locations:
The intersection of the new construction geometry and sketched lines or curves.
The intersection of the new construction geometry and existing construction geometry.
The intersection of the new construction geometry and reference geometry. ABAQUS/CAE displays preselection symbols only when the reference geometry was created before the feature being edited. (See “Reference geometry,” Section 19.5.1, for more information about the behavior of reference geometry.)
Construction lines also define the axis of rotation when sketching revolved solids and surfaces. For more information about the relationship between construction lines and the axis of revolution, see “Defining the axis of revolution for axisymmetric parts and for revolved features,” Section 11.13.5.
Construction geometry is shown using dashed magenta lines to distinguish it from sketched geometry. Construction geometry is visible only while you are working on a sketch; as soon as you exit the Sketcher, the construction geometry disappears. ABAQUS/CAE saves construction geometry with the original sketch; if the Sketcher is invoked to modify a sketch that included construction geometry, the construction geometry reappears along with the sketch.
To create construction geometry, select one of the construction geometry tools from the Sketcher toolbox or select Sketch
Construction from the main menu bar.
Figure 19–7, Figure 19–8, and Figure 19–9 illustrate how construction geometry and preselection combine to help you create the desired sketch. In this example the user is creating a sketch of a connecting rod.
Create two construction circles (indicated by dashed magenta lines), as shown in Figure 19–7.
Sketch two fillets tangent to the construction circles (indicated by green lines), as shown in Figure 19–8.
Sketch two circular arcs (indicated by yellow lines); a preselection symbol indicates the vertices at the ends of the fillets when you move the cursor close to them. The arcs are centered on the center of the construction circles and extend between the vertices, as shown in Figure 19–9.
