US Army Corps of Engineers

The United States Army Corps of Engineers is a U.S. federal agency under the Department of Defense and a major Army command made up of some 37,000 civilian and military personnel, making it one of the world's largest public engineering, design, and construction management agencies.  Their logo is a Red Castle and they have a location in Greencastle, Indiana, two hints Q dropped back in 2018.  POTUS will use the US Army Corps of Engineers to build the wall along the southern border.