If you are building a one of a kind deck or bridge jigs are not really necessary. You can make a spacer to align deck ties in both cases.
If you build a lot like I do then a glue jig for the deck ties is the fast an easy way to go. Among other things it ensures all decks are the same exact width.
I have no photos of my jigs handy but all consist of dadoes cut into plywood that fit the deck chords. I cut shallow dadoes on the chords that accept the deck ties so there is no need for spacers. The chords are placed in the jig and the ties are glued in place with white wood glue.
For truss / girder bridges I have diagrams that show where the vertical posts go for the standard sizes. I attached a sample pdf.
Below are some photos
Joe
