We dont work the Tracing boards in Ireland, but I use them in my own philosophical, introspective musings (try saying that with a few drinks!). The Entered Apprentice is offered these set of symbols to focus their thoughts and guide meditation.
As Dr Lomas states
"The floor represents the physical state, or our material bodies, the lower or material nature. The sky with it's Sun, Moon and Stars stands for the mind, or intellectual nature. But the blazing Star, or glory, represents the ultimate spiritual core"