This flag determines whether this projectile can be stopped by walls in its path. If set, the unit firing it will only fire once it finds a firing location not obstructed by walls.
Mind that weapons with warhead set to Wall=yes
will be able to target over walls even if SubjectToWalls says it shouldn't. Weapons with a moving projectile will then hit the wall, however weapons with invisible instant travel projectiles, such as Tesla, Prism and bullet weapons will be able to fire past the wall. Tesla and Prism have a projectile image because of IsElectricBolt=yes
graphical effects tags, the projectile itself is still invisible.