The cables must be flattened against the metallic frames of the box in order to
minimise the frame loops and thus benefit from a disturbance screening effect.
If the box is made of plastic and the loads particularly sensitive, it must be replaced
by a metal box.
In all cases, you must check that the metallic frames of the boxes or cabinets are
frame grounded by very short connections.
Finally, if screened cables are used, extra lengths which serve no purpose
("pigtails"), must be cut off as they reduce screening effectiveness.