Abstract: A plug designed to seal an opening formed in a concrete wall. The plug comprises a main body portion, a first end, and a second end wherein the first end and second end are combined by a bolt having a fastener on one end. Washers are combined with the bolt on each end of the plug. The plug has a first diameter wherein it can be inserted into the opening and a second diameter wherein it plugs the opening in the wall. The plug is moved from its first position to its second position by tightening the fastener thereby squeezing the plug between the two washers. This tightening causes an expansion of the plug to its second position, increasing its diameter inside the opening and forming a seal between the plug and the wall of the opening.