Once the approximate binding sites and the clamping type are chosen, the binding sites need fine tuning. The goal is to minimize primer self dimerization. We usually start with the optimization of the forward primer. This is already the default setting and can also be selected by hitting ``1''. The dimer formation for the selected primer can be watched in the lower part of the screen. All dimers are shown in a list which is sorted in decreasing order of significance. Clusters of hydrogen bonds at the 3`-terminals of the primers are highly unfavorable and appear at the top of the list to catch the eye. The bonds are displayed as thin (AT) and thick (GC) yellow rectangles. The primer can be moved using the cursor keys until a position is found, where self-priming is negligible. The ``+'' and ``-'' keys are used to vary the annealing temperature. The primers are automatically lengthened or shortened using the nearest neighbor algorithm. Simultaneously pressing an arrow key and the control key (ctrl) causes the primer to jump to the next acceptable position. Once the forward primer has been determined, a suitable reverse primer must be found. This is initiated by pressing ``2''. It works the same, except that not only the self dimers but also dimers between the forward and the reverse primer must be observed.