Sizing

If you are using the template provided in the SS3D Modeler's Kit, then hurray! The sizing should already be obvious to you.

A square in the checker grid is the size of a tile in SS3D, but even if you aren't using the template, a square in Blender's default grid is the same size.

You should take care to ensure that a 1x1 sized object fits slightly within the confines of a grid space, so that it does not collide when being slid through doorways.