The light from the spotlight shines through.

@CloakPin I tried it and it didn't work.

@CloakPin I made a box out of fuel tanks and the spotlight was supposed to shine there, but the box let the light through.

Just tried it.
I have no light passing through any details.
What are you able to make it pass through?

Change its intensity i believe.
I havent played with it in years but you used to have to create two layers of building to stop the light from going through objects