Scout Factors for Secret Doors

How do I factor a Scout test for a character looking for secret doors?

The skill entry for Scout lists factors for finding trap triggers, but not for secret doors. Searching for examples, I noticed that both the Dread Crypt of Skogenby and the House of Three Squires feature a secret door. The obstacle for the Scout test in both cases is 3.

Is this based on the factors for location (“location is ‘in that direction over there’ ” [3])? What’s the best way to factor this?

What do the characters know about the location of the secret door when they start searching for it? Do they know where it is? (e.g., did they see someone use it but it closed before they could reach it?): Ob 1 (location known). Do the have a pretty good idea of where it is? (e.g., they saw someone head toward a particular area of the chamber before their lights went out and he was gone when they relit the torch?) Ob 2: location roughly known. Do they just have a suspicion there might be a secret door here? (e.g., they searching because they’re certain the hallway can’t dead-end here?). Ob 3 (location is “in that direction over there.”)

Thank you for the breakdown.

BTW, I love how easy it is to search for secret doors (which are most fun if found) compared to traps (which are most fun when they go off in a twist).