Axis addon blender
This addon is to make an axis to help to align objects.
Download the addon and install it
In edit mode in the menu 'edit' the options appear.
'Axis through plane' - creates an axis at the weigthed center of the plane, perpendicular to the plane.
'Axis through three point' - select tree points if a circle and an axis is created in the center of the circle and perpendicular to the circle.
'Cursor at axis' - pust the 3d cursor at one of the points of the axis (can be swaped), the direction of the cursor is addapted to the axis direction. If you create a new object at the cursor possition and choose 'align- 3D Cursor', the new object is in the direction of the axis.
(be aware that the rotation has to be aplied in object mode)
'Remove axis' - removes all axis in this object.