How do I build a round arch?
Set the outer width and how high the arch should rise. A half circle rises half as high as it is wide; lower values give a flat arch for long bridges, higher ones a tall arch for gates. Then build the chart row by row from the bottom, starting on two pillars.
How wide is the opening under the arch?
The width is measured across the outside. Subtract twice the thickness to get the opening: an arch 15 wide with thickness 2 leaves an 11-block opening. For a 3-wide opening with a 2-block band, enter 7.
What do Thickness and Depth mean?
Thickness is how wide the curved band is, seen from the front. Depth is how many slices you place behind each other, which is the thickness of the wall or the width of a bridge. The chart shows one slice; the totals are multiplied by the depth.
Should the width be odd or even?
An odd width is centred on one block, so the crown has a single keystone in the middle and the opening is odd (1, 3, 5 …). An even width has a 2-block centre and an even opening. Match it to your door or road; the Odd/Even button switches between the two.
Can I build a bridge with it?
Yes. Set Depth to the width of the road and the rise to about a quarter of the width for a flat span: an arch 31 wide with a rise of 8 needs 68 blocks per slice. For a long bridge, repeat the arch with pillars in between.
Why are the lowest rows straight?
Near the bottom, the sides of a half circle are almost vertical, so the first rows of the chart stack straight up before the curve begins. That is correct: it is where the arch meets its pillars.
