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make sure

make sure idiom

Make certain, establish something without doubt, as in Make sure all the doors are locked. It is also put as make sure of, as in Before you make that speech, make sure of your facts. This usage was first recorded in 1565.
make sure of. Act so as to be certain of something, as in He wanted to make sure of his own district before seeking support elsewhere. This usage was first recorded in 1673.

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.