Ralph Mowery wrote:

wrote in message
...
Please provide the cite for that. And explain why if
it's not permitted, why major panel manufacturers have listed
lockout slides for their panels, for exactly the purpose I
outlined?


The sad thing is that those plates and about 3 screws and nuts cost from
about $ 50 to $ 100. Should be less than $ 20 for what it cost to make
them.

$8 along side the optional grounding bus bars and other panel
accessories. Perhaps they'll get there eventually as they become more
popular and thus have more sales volume.