Replacement and Close Placement

The Third Instruction is Replacement
If the mind forgets and wanders outwards, mindfulness and alertness immediately recognize it and return the mind to resting Upon its object as before.  In this way movement is brought right back to stillness.  This is called Replacement.

The Fourth Instruction is Close Placement 
When meditating with mindfulness, focused on an object, and subtle underlying movement occurs, you regenerate the power of the previous mindfulness.  As your mind remains focused on the object, this is called Close Placement.

Excerpt of text written by Khenpo Karten Rinpoche, from the book Precious Teachings, chapter entitled “Nine Instructions for Concentration Meditation,” page 110 in the paper book, and page 118 in the PDF version.