I Smell a Rat battle maps (spoilers)

[Dalin]

Had an impromptu game today with a few new players who were intrigued by the box on my coffee table. Had a blast, though we only barely started; we enjoyed a rousing battle with the spiders. This battle, however, made me realize that despite gaming for 35+ years, I don't know how to properly use preprinted combat scale maps. I always drew everything on a wet erase mat or, in recent years, dispensed with scale grids and ran things TotM-style, with occasional visual aids and sketches on a whiteboard.

My confusion centers on the fact that the maps give away the locations of secret doors, hidden passages, illusionary walls, etc. I could cover a wall, but that's not too subtle. Covering all the walls is possible, but awkward, especially with people reaching over to move their figures each turn. When I unfurled the map for the spider battle, I naively expected to see a for-the-players version without the smuggler' den or concealed passage.

What's the standard way to use aids like this? Just tell the players to role play what their characters would know?