Abstract: A railway car side panel assembly with upright support posts forming the side walls of the car wherein painted or galvanized panels are protected from rusting by plastic inserts positioned between the corners of the panels and metal brackets on the posts to prevent vibration-abrasion of the galvanizing or paint and of the corners to rust, the plastic inserts being of flexible plastic material and formed as envelopes pocketing the corners and fitting into the complementary brackets, said envelopes each having a side wall with a retainer bottom snapped over flange edges of the panel to hold the envelope from falling off during assembly with the brackets.