Bridgeport 978 3 IN Edge Type Conduit Clamp, Box of 5
https://nsiindustries.com/product/edge-type-conduit-clamp-3-malleable-iron/
Bridgeport Edge Type Conduit Clamps are used for running rigid, intermediate metal conduit (IMC) and electrical metallic tubing (EMT) across or perpendicular to beam, channel and angle supports.