None U-Shaped (.281) E.I.A. Punched 11 ga. C.R.S. L-Shaped (.281) E.I.A. Punched 11 ga. C.R.S. L-Shaped 10-32 Tapped 11 ga. C.R.S. Tel. Ind. Rails L-Shaped 12-24 tapped 11 ga. C.R.S.