I cringe whenever I see this type of electrical connection. Someone needed a 30 amp, 240-volt electrical receptacle outlet for a floor sanding machine. Except for electric clothes dryers, that type of circuit is rare in residences.
To get power for the floor sanding machine, it is a common practice to remove a few circuit breakers, say a prayer, and then clip directly onto the main busbars without any fault and overload protection or personal protection equipment. It is not electricians doing this; it is the floor-sanding people who should not put their hands into a live electrical panel.
I have also seen welders do this on commercial construction sites to get power for their electric welders.
The alternative is to have an electrician install a new circuit and electrical receptacle outlet for a few days of equipment use.
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