no, zoom in, there's a bevel on one side
If you put a pair of side bars for one frame down flat on the table with the groove for the foundation facing upwards, you will have one bevel facing to the right and the other facing to the left.
If you have two of either right hand or left hand sidebars and construct the frame with (if you put the finished article flat) one bevel facing up and the other facing down, you will find that one of the grooves is on the outside of the frame, if you, with the same two side bars) construct it with all the grooves facing inwards as they should then you will have both bevels facing the same way
I'm sure that's incorrect, but I'd be fascinated to be shown to be wrong if you have time to post a photo at some point.
I buy my sidebars in fifties and never think to consider which side goes where. I just pick them up and stick them on and they "just work". If I've got it right every time over thousands of frames purely by chance I shall be buying a lottery ticket next week.
James
try it tomorrow James, then have a stiff drink and a lie down