At times, geometry might interfere with your ability to infer points from other points, making it difficult to draw accurately. Use an inference lock, which tells SketchUp not to waver from the direction it is currently inferring from, to solve this problem. To use the inference lock, press hold the Shift key when SketchUp infers the desired alignment (the inference line will bold). The alignment will remain locked, even as you move the mouse and/or pick a secondary inference point. The following image shows the inference locked in the blue direction to ensure that a new line is exactly perpendicular to the face.
Any of the inference conditions may be locked; along an axis direction, along an edge direction, on a face, from a point, parallel or perpendicular to an edge, and so on.
Forcing an Inference Direction
You can force SketchUp to infer parallel to a specific axis by pressing one of the following keys while using the Line tool, Move tool, or Tape Measure tool:
- Right arrow key = red axis
- Left arrow key = green axis
- Up or down arrow keys = blue axis