The Ortho Setting constrains the cursor movement to vertical and horizontal directions. This feature allows you to quickly specify straight line segments for rooms, drawing entities, objects and calculation grids.
-
Ortho Mode can be toggled On or Off from the Switches Toolbar or by toggling the F8 key on your keyboard.
-
Ortho Mode is transparent, which means that it can be accessed at any time without breaking the current command.
Select
the Ortho button on the Switches
toolbar 
. or
press F8 on your keyboard