What's the Title of This Haunted House Book?

Long ago I read a haunted house book published in the 1970s (or perhaps much earlier?). I don't remember the title. 

A group of people gathered to investigate a haunted house. They thought that some rooms might be sealed off. So they hung towels from every window, then checked from outside to see if any windows had no towels (indicating the door to that room had been walled up and hidden from them).

2015 World Horror Con Badge Holder Crumbles Into Dust

I've attended dozens of conventions these past 24 years. I keep all my convention badges in a tote bag in my closet. Today I examined my bag's contents, which I haven't done in many years; I just drop in the new badges.

My 2015 WHC badge holder appeared intact. But when I picked it up, it crumbled to my touch. All my other badge holders are fine.

What was this badge holder made of, paper? My 2015 WHC tote bag has a similar orange appearance (I also keep my convention tote bags), yet it remains intact and firm.

I screened several Tabloid Witch Award winning horror films at the 2015 WHC in Atlanta. A great event. 

Anyone else miss WHC?

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