a mounting plate having an aperture to provide a passage therethrough;

a guide slot;

a spring clamp structure displaceably engageable with the guide slot;

two or more spaced-apart retention formations in the mounting plate disposed at predetermined spaced locations adjacent to the guide slot;

the spring clamp structure having a spring support bracket, the spring support bracket having a bottom retention base displaceably retained captive by the guide slot;

a spring biased clamp arm secured to the spring support bracket, the spring support bracket having a securing sleeve slidingly couplable to the two or more spaced-apart retention formations, the securing sleeve having one or more arresting formations at a lower end thereof for retention coupling with selected ones of the two or more spaced-apart retention formations disposed spaced-apart along the guide slot;

the spring support bracket being displaceable along the guide slot with the securing sleeve disposed at a disengaged position;

the spring support bracket being securable along the guide slot with the securing sleeve disposed at an engageable position,