Trying to make a laser beam trip alarm/explosion

I was following along with this YouTube Video on making a Laser Trip Mine so I could instead make a Laser Beam Trip Alarm. I need to know how to get around the fact that instead of going one direction along the X-Axis with my Collision Box it will extend out from center out both directions. My blueprints and everything are exactly matching and I think it has something to do with how UE4 Engine 4.15 has changed since 4.7 which the video uses.