I have a few 3/8" double expansion concrete anchors and noticed that on one side it is threaded and on the other it is not.

Which side goes into the hole? Double Bolt Anchor


2 Answers 2


It looks to me that the threaded end should go into the hole first. As the bolt is used to cinch the mounted item the back of the mounted item will compress the front side of the expansion anchor toward the threaded part while at the same time threaded part pulls forward to expand the anchor in the hole.

  • That's what I do. Otherwise, the unthreaded wedge wouldn't have any force on it.
    – George
    Sep 18, 2017 at 3:34

According to Confast, one manufacturer of such anchors, you are supposed to:

"insert the double expansion anchor with the nut first into the hole"

By "nut first" I believe the narrator must mean the threaded end.

(Source: https://youtu.be/LNz6IaM9BK0?t=102 linked to from https://www.confast.com/how-to-install-double-expansion-anchors)

The Confast anchor looks pretty much identical to the example asked about. Curiously they only address this important installation detail in their video, and not in the written instructions or diagram which they also have online.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.