Answers for "how to increase border length in css"

border width css

.element {
  border-width: 2px;
}

border width css

element {
	border-width: 10px;
  	/* Or use shorthand border property */
  	/* width style colour */
  	border: 10px solid black;
}

how to set border length in css without div

div {
  width   : 200px;
  height  : 50px;   
  position: relative;
  z-index : 1;
  background: #eee;
}

div:before {
  content : "";
  position: absolute;
  left    : 0;
  bottom  : 0;
  height  : 1px;
  width   : 50%;  /* or 100px */
  border-bottom:1px solid magenta;
}

border width css

#some-div {
  /* [WIDTH] [FILL MODE] [COLOR] */
  border: 5px solid #f00; 
  
  /* draws solid a red line of 5px
  between the padding (inside the div)
  and the margin (outside the div) */
}

border-width in percentage

You can not set Border Width in the Percentage its the rule 
But you can able to do this just by wrapping into a new div 
and in most of the cases you did not need that

how to change border height in css

ul {
  list-style-type: none;
  display: flex;
  flex-direction: row;
}

li {
  padding: 10px;
}

.custom-border {
  position: relative;
}

.custom-border:after {
  content: " ";
  position: absolute;
  border-left: 1px #6c757d solid;
  top: 35%;
  right: 0;
  height: 30%;
  margin-top: auto;
  margin-bottom: auto;
}