Living in a condo has a distinct disadvantage on Halloween. Everyone's porch lights are on 24/7 so you can't tell who has candy.
To flag down passing trick-or-treaters, I made this sign to hang on our door. The size was determined by the bed size on my original 3D printer, a Cube 2 by 3D Systems.
Feel free to download the .STL file below, scale up the sign, change colors, and share with your friends. Just remember to post pictures of what you made and let me know if you have any problems.