@aukuras said: My model needs an accuracy of 0.001mm What are you modeling?

To make the R segment follow a curve in the Z plane, you can use the Follow Me tool in SketchUp. Here's how: Draw a line from point A to point P to create segment R. Draw a curve in the Z plane (curve H) that the R segment should follow. Use the Follow Me tool by selecting the R segment and clicking the Follow Me button in the toolbar. Click on the H curve so that the R segment follows the curve. Once the R segment follows the curve, use the Face Intersect tool to create a clear intersection between the R segment and the curve. Using the Follow Me tool, you can make the R segment follow any path or curve in the Z plane. Follow Me Tool Examples in SketchUp - The SketchUp Essentials #39 regards web designer WorkTime company

@aukuras said: I need high precision... I think the best approach then is to model it at the correct length from the beginning and avoid introducing errors by modifying the incorrect shape.