Hi Ken,
I created a layer that I quite like for symbolizing barbed wire fencing. It's a basic black line then 2 point marker layers are added in the structure tab. Search for and set both markers as arrowhead 7 and set the angle for the second to 180°. I find setting the endings for the marker placements to No Constraint works well for me.
ChristopherBertrand_0-1622044725364.png