Check out example codes for "how to make hr class bootstrap full width". It will help you in understanding the concepts better.

Code Example 1

/* It is done with the <hr> tag. Then you need to give it a class name, and adjust the margin accordingly. See below for an example. 
  */

.solid {
  margin: 0 -15px;
  border: 0;
  border-top: 1px solid #c9c7c7;
}

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