How do I give a cutting board or sign blank matching curved (arched) edges on every side?

The idea

Dragging each side into a curve by eye never gives four matching edges. The reliable method uses an offset copy of the rectangle as a guide, then turns each straight side into an arc that snaps to that guide. Every side bulges by exactly the offset distance.

Steps

1. Draw a rectangle the size of the board measured at its corners.
2. Select it and use Offset Vectors to make an outward copy. The offset distance is the arch depth, meaning how far the middle of each side should bow out.
3. Select the original rectangle and press N to enter Node Editing mode.
4. Hover over one straight side (a span). Right-click and choose the option to convert the span to an Arc. The menu shows the shortcut key beside the command, and educators use the A key for it.
5. Click and drag that arc outward. Dragging an arc span changes its radius while the two end nodes stay where they are. Let it snap onto the offset guide line.
6. Repeat for the other three sides.
7. Press N to leave Node Editing, then delete the offset guide (or move it to a hidden layer).

The corners remain in their original positions, and each side now crests exactly on the guide.

Variations

• Arch only the two ends: convert just those two spans.
• Inward curve: make the offset inward and drag the arcs to it.
• Softer corners: add fillets after the arcs are made.

Pro tips

• If a node jumps to the wrong place while dragging, zoom in. Snapping picks the nearest candidate under the cursor.
• Holding Ctrl while dragging an arc or Bezier span moves the whole span instead of reshaping it, which is not what you want here.
• The same right-click menu converts a span to a Line or a Bezier curve, inserts a point, or cuts the vector at that spot.
• See the entries on node editing and on the Offset Vectors tool for more detail on each tool.