Preventing “double” borders in CSS

Question

Say I have two divs next to each other (take https://chrome.google.com/webstore/category/home as reference) with a border.

Is there a way (preferably a CSS trick) to

Answer 1

My use case was for boxes in a single row where I knew what the last element would be.

.boxes {
  border: solid 1px black  // this could be whatever border you need
  border-right: none;
}

.furthest-right-box {
  border-right: solid 1px black !important;
}