u lay them just like other objects, but put them as close to the middel and set the x and y axis to 25, or 75. but bridges, then u only set one of the, if the bidge is going from west to east, then u only change the x axis. and with bridges u gotta have t y axis the smae, of course, cause that's how high the bridge is gonna be, on forest u only use "fit to ground", but that doesn't allways work though
Garcia