Lay out Tutoral

[harry strasil]

To check and see if a sheet is cut square.



1. Go to any corner and select a pivot point shown by the ARROW and put an X.

2. Using a trammel or large compass, scribe Arcs A, B on the bottom edge and C as shown, all with the same setting on the trammel or compass.

3. Using a straight edge draw a line thru the pivot point and where Arc B meets the edge of the sheet so the line crosses Arc A.

4. Using the straight edge again, draw a line thru where C meets the edge and where the first line and Arc A cross.

This will be a perfect square.

[Bill Huber]

Isn't that about the same as the 3,4,5 way to check square only using a compass and not a ruler?

[Harold Burrell]

To check and see if a sheet is cut square.


1. Go to any corner and select a pivot point shown by the ARROW and put an X.

2. Using a trammel or large compass, scribe Arcs A, B on the bottom edge and C as shown, all with the same setting on the trammel or compass.

3. Using a straight edge draw a line thru the pivot point and where Arc C meets the edge of the sheet so the line crosses Arc A.

4. Using the straight edge again, draw a line thru where C meets the edge and where the first line and Arc A cross.

This will be a perfect square.

Man...I should have paid more attention in geometry class...

[harry strasil]

Isn't that about the same as the 3,4,5 way to check square only using a compass and not a ruler?

Yes Bill, but the 3,4,5 method of measuring only does that, tell you how far off it is. By using this method you end up with a true reference line.

Harold wrote:"Man...I should have paid more attention in geometry class..."

Harold, this method is out of an 1885 or 89 sheet steel and copper smiths book I own.

[Bill Huber]

1. Go to any corner and select a pivot point shown by the ARROW and put an X.

Got that one, its easy.


2. Using a trammel or large compass, scribe Arcs A, B on the bottom edge and C as shown, all with the same setting on the trammel or compass.

Got this one, no problem.


3. Using a straight edge draw a line thru the pivot point and where Arc C meets the edge of the sheet so the line crosses Arc A.

This one I am having a problem with. I don't see why you need to draw a line from C across the pivot point. I don't understand how it will cross arc A. Shouldn't it be draw a line across B to A though the pivot point?

4. Using the straight edge again, draw a line thou where C meets the edge and where the first line and Arc A cross.

This one I understand.

circle 1.jpg


You can do the same thing with the 3,4,5.

1. Pick a point (P-1) and set the compass at 3 units and make and arc (3)
2. From the same point (P-1) set the compass at 4 units and make an arc above the point (4).
3. Set the compass at 5 units and set the the point were arc 3 hits the edge. Draw the arc though arc 4.
4 Draw a line from P-1 though the point that arc 4 and arc 5 cross. This will give you a 90 degree line to the base.

I say units because it can be ft. in. mm. m. miles what ever.

circle 2.jpg

Your way is a faster way to do it and you only have one setting on the compass but it can be done with 3,4,5 also.

[tim rowledge]

There's an even easier way if you have a suitably sized sheet of paper with a reliable straight side -
Fold paper roughly in the middle of the straight side so that the folded over edge matches up neatly. The edge with the fold is now at 90deg to the reference edge. Hold paper against wood to check for square.

For extra credit, fold the piece of wood

[harry strasil]

My Bad Bill, it has been corrected, and how do you get a perfectly straight line with the 3-4-5 method so that the 5 segment line is right.

Oh Well, I was just trying to help.