My favorite for hanging steel - Caldwell T-Post Plate Target Hanger

Caldwell is an excellent brand that has been around a while and for good reason. This simple yet well executed design is great for hanging steel plates with a center hole from t-posts. It is very sturdy as it is made of high grade steel and attaches securely to the t-post with bolts that thread through the unit. The bolt up top with the tension spring holds your steel target away from the t-post and allows the steel to give when impacted to direct bullet spalling downward in a safe direction. I've put hundreds of rounds on steel mounted to these and have never had issues with them not holding up or having anything come back my way. I highly recommend.