These are 1x1, 2x2, and 3x3 OpenForge stone floor segments, each of which contain a trap door.
They print without support on my Printrbot Simple 2014.
The pieces are completely compatible with OpenForge and DwarvenForge as 1x1, 2x2, and 3x3 stone floors.
Thanks to my Patreon supporters for their contributions, which made this piece possible.
Printed without support on my Printrbot Simple 2014.