Water Gardening: Flirtations with Filtration, 1 by BogweedBuck

BogweedBuck wrote:
After tracing the insde of the hole, I drill a small pilot hole at the very top of the circle that was traced with my marking pencil. That allows me to re-trace the hole on the outside of the bin so it is easy to line everything up. Cutting the hole out from the inside with a jigsaw would be a pain.

Aligning the inner-top part of the circular hole from the ducting hood immediately over that hole I drilled, I retrace the circle around it's outside diameter.