The fence around the moon

Is sometimes hard to see, but a
wooden post & rail fence runs
rings around the moon. There's
a minimal gap between the fence 
& the lunar surface that deters 
goats or other space inhabitants 
from pushing beneath it. A var-
iety of media — plasma bursts,
lithium batteries, ouija boards, 
Barbra Streisand recordings — 
were tried, but none proved as 
efficacious as wood in keeping 
polka dots out of its displays.