Select the 'Annotation New' button from the Linear Draft toolbar and follow the prompt to select the first structure to annotate.
After selecting the first structure, follow the next prompt
Once the second structure has been selected, the span & versine will be automatically calculated and input into your model (assuming that they are located along the same tracks).
If this selection is for a structure that covers multiple tracks (like in the example below), then all tracks span & versines will be added.
You are able to continue adding span & versine values along a track length with each click on a structure, this will add in the values between the structures that you choose.
The 'Select Second Structure' prompt will remain visible until you cancel the action (by right-clicking or choosing another command).
N.B. Span & versine values will not be displayed if the span track alignment is made up of broken lines.