Put it back as you took it out, after cleaning. As you see the two metal forks on the side of the mag, they are slanted toward the front of the mag. You have to use a scratch-awl or ice-pick that is very narrow, push it up into the hole in the bottom of the baseplate, when it pushed the metal with the fork attached, parallel to the baseplate, it will snap into place. Dealing with these magazines I wonder why I clean them so often, habit I guess. They are very poorly designed. I bought my Shield for Christmas, just tried it out, shoots great, but the extended mag is better, but I had trouble with both magazines. The smaller one the dimple inside to lock the mag, doesn't match with the baseplate, got to go to the manufacturer