You select a route by choosing first a start block and then a destination block.
The selection of the block is the same: move the mouse pointer over the desired block on the diagram and click the left mouse button. If you selected the start block, the diagram will change by dimming most elements but highlighting possible destination blocks (yellow for direct execution, orange for stackable executions), while the starting block will be even dimmed further. You then repeat the selection for the destination block, after which the display turns back to normal. If successful you will see the route being set, the switches thrown and the signals cleared. If not, a message will appear in the info line, and you may want to stack the route for later execution.
Instead of a block, you can select and click on a signal as well. On a start block, however, only routes passing this signal will be considered, not any routes leaving the block at the other end. On a destination block you can select signals at either end. Stub tracks may have visible end-of-track signals on the diagram at the stub end. Such signals can also be used to indicate the destination block, but never a start block.
For an alternative way to select a route using the numpad see here.
This process is the same whether you create or cancel a route. But to invoke the cancel route function, you must have the “Cancel Route” option active in the “Special Commands” panel. Furthermore, you must have set all signals to stop that are part of the route to be canceled prior to canceling the route (Note: automatic signals not visible on the screen will be set to stop automatically). Finally, only destination blocks are highlighted that are eligible as destinations from the start block of the route to cancel. Stacking is not possible. The “Cancel Route” option is automatically deactivated after the destination selection, independent of whether the route cancellation was actually successful or not.
Tip: If you selected a start block, CTC expects the selection of a destination block. If you want to back out of this process, simply press any regular key on the keyboard, e.g. <ESC>. You can also click the start block again or any other block that cannot be reached, but clicking the start block is the safer way, since start block and destination block can never be the same.