Abstract: An expansible anchoring plug for anchoring by impact in undercut pre-drilled holes, especially in holes which are widened towards their inner end, comprises an expansible sleeve which has an internal bore and which it is slotted over a part of its length and which can be anchored by driving it onto an expander body provided with an expander cone located at the bottom of the pre-drilled hole. The expander body is provided with a tubular extension engageable in an internal bore of the expansible sleeve. The end of the extension, once the expansible sleeve has been driven onto the expander body, is located in an enlarged portion of the internal bore of the expansible sleeve and is secured therein by a wedge.