Making these decorative rings is a quick way to hide water pans under potted houseplants. They also work well for stabilizing your dog's water bowl so it doesn't get tipped....or kicked in my case. This is a quick and easy project if you have a miter saw for cutting the angled ends. Alternatively you could also use a table saw or cut each piece with a hand saw (good luck). Here's how.
Step 1: Let's Do Some Figurin'
The first step is to decide how wide your octagon needs to be. Place 2 straight edges on either side of the pot or bowl and measure between them. This measurement is the minimum width for your ring. In most cases, I'd recommend adding 1/2" to your measurement to allow for a 1/4" of space on each side. That's it for the math, now we just need to make some drawings.
How to draw an octagon (pic 2)
Taking your width measurement+1/2" and draw a square with each side equal to that length.
Draw an "X" by connecting the corners diagonally with a line.
Place your compass point on a corner of the square and draw an arc 1/2 the length of the diagonal (from corner to center of square). Repeat for each corner.
Simply connect the ends of the arcs and you have an octagon.
To be an octagon, all eight sides should be equal when you're done. The drawing you made is an optical illusion as the angled lines appear shorter, but in fact they are all equal. Measure one of the sides. This is the length of your 8 pieces along the inside edge of your ring. In pic 3 you can see the side pieces are actually longer than this measurement because of their angled ends. Just remember to draw your cut line on the edge that will be inside the octagon. If you mark your cuts on the outside edge or face of the wood, your octagon will be too small.