Mains Cable Support at Rear of Box

When the mains cable goes into the back of an amp, CD Player etc., it sometimes sags so that the plug is not fitting tightly. What are people's solutions for this?

This sagging can be caused by the weight of the cable or perhaps a loose fit. I've no idea if this sagging has any negative effect on sound. (this post is not about the sonic merits of cable supporting blocks).

In the past I've used a block of wood, or string tied to a hook (adjustable like a hood on a jacket).

 

I've started making my own mains cables and use Wattgate terminations. The U.S. IEC models I've used have a small cutout opposite the ground that you can insert a provided small tube to nullify the sagging.