Suppose there is an angled line and an object that needs to be rotated to be parallel to that line, what are we gonna do?

We could first measure the angle of line and then rotate the object the measured angle, but the result would be subject to tolerance if the measured angle is not an integer.

Use R parameter in Rotate command

Select the object to be rotated, enter RO command, then press Enter key, shown as below,

After executing the Rotate command, the CAD system will prompt users to specify the base point, we can specify the left end point of line as the base point, we can that when we move the cursor, the rectangle moves around the specified base point, shown as below,

Then enter R and press Enter key, you’ll be prompted to enter the reference angle, the default reference angle is 0, which is horizontal, and because the rectangle is horizontal, so we can just press Enter key, then the software will prompt users to enter new angle, shown as below,

The last step is to pick the right end of the line when prompted to enter new angle, the rotation is finished once you’ve picked up the right end of line