By default, drawing guides have no effect when using the Eraser tool. If you want, you can enable using the Eraser tool with guides.
How to erase using a Drawing Guide
- In the Guides view, click on the
Enable Guide with Eraser button to toggle it on.
The 
Eraser tool will now work with the currently selected guide, just like the 
Brush, 
Pencil and 
Line tools
- Start erasing.
NOTE When this option is enabled, it is also possible to make adjustments to your guide while the Eraser too is selected.