Use Quarter Cross 
to place quarters of a full crosses 
in the corners of grid squares, and erase quarters of grid squares. Use single-click to place or erase one at a time, or drag to draw continuously. A quarter cross is placed in the corner of a grid square nearest to the point where you click.
Note: It may be useful to Zoom In when working with quarter crosses.
If part of a half cross forward or half cross backward is replaced or erased, a quarter cross is left in the other part.
To Place a Quarter Cross
-
Select Quarter Cross
in the Create window 
, then click or drag on the work area to draw or replace crosses.
Note: Select Erase 
or press the Option key when drawing to erase crosses.