# How can I find the centroid of a trapezoid with equal angles at the ends? [closed]

Trying to find the center of a trapezoid with beveled edges and there are 153 holes to be drilled. I know the easy way would have been to find it before I made the bevel cut but I wasn't thinking clearly I guess.

• How are the bevels an impediment? By "equal angles at the ends" do you mean that it's symmetrical? What material are we talking about? What does hole quantity have to do with this? Please revise to provide more detail about your problem. Commented Aug 19, 2022 at 14:16
• What are you actually trying to do?
– JACK
Commented Aug 19, 2022 at 15:11
• That's a lot of holes. Why not start over with some raw source material that's built with hole patterns (as is, e.g., pegboard)? Commented Aug 19, 2022 at 15:21

A picture would help, but assuming it's reasonably sized you can enclose it tightly in a box slightly higher than the bevels, and use the inside walls and corners of the box to find the center. Or you could mark it out on the floor or table and use the markings as a template for your holes. Basically the same thing ... just work around the bevels.

Mass centre:

Hang it by one corner and draw the perpendicular line, the another corner and repeat.

Centre is where they cross.

To get the perpendicular line either use a plumb bob (that may confuse some) and draw a chalk line (pinging chalked string is an easy solution) or a level to get the vertical.

• Why not just call it "a vertical line"? This seems like a very cumbersome strategy. Commented Aug 19, 2022 at 14:15
• This is doing things the hard way. Since the OP says the trapezoid is symmetric, dropping a couple vertical lines with a T-square will do the job. Commented Aug 19, 2022 at 15:20
• Solar Mike's process works for any shape object, regular, irregular, with or without holes, etc. Commented Aug 19, 2022 at 15:24
• This process will not work if there are off-center or uneven holes. Otherwise, I'm 100% for it. Commented Aug 19, 2022 at 15:48