Using The Opposing Outward Face Orientation Option
Selecting the Face Orientation option, Opposing Outward, provides an imprinting mode which ensures that only faces that are facing each other with opposing outward normal directions are imprinted or merged.
When imprinting thin, penetrating parts, the imprinter can choose the wrong side of the destination part with which to imprint or merge the source part.
The following geometry shows two parts that intersect each other.


When these parts are imprinted with the Opposing and Aligned option selected, the surface of part 2 is imprinted onto the wrong side of part 1.


If these parts are imprinted with the Opposing Outward option selected, the surface of part 2 is imprinted onto the correct surface of part 1:

