Generated by SassMeister.com.

SassMeister-input-HTML.html

<ul class="solutionThumbnails">
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
</ul>

SassMeister-input.scss

// ----
// Sass (v3.4.14)
// Compass (v1.0.3)
// Susy (v2.2.5)
// ----

@import 'susy';

.solutionThumbnails {
  @include container(24);

  li {
    @include gallery(6 of 24 split);
    background: #666;
    display: block;
    height: 240px;
    margin-bottom: 1em; // for viewing only
  }
}

SassMeister-output.css

.solutionThumbnails {
  max-width: 100%;
  margin-left: auto;
  margin-right: auto;
}
.solutionThumbnails:after {
  content: " ";
  display: block;
  clear: both;
}
.solutionThumbnails li {
  width: 24.16667%;
  float: left;
  background: #666;
  display: block;
  height: 240px;
  margin-bottom: 1em;
}
.solutionThumbnails li:nth-child(4n + 1) {
  margin-left: 0.41667%;
  margin-right: -100%;
  clear: both;
}
.solutionThumbnails li:nth-child(4n + 2) {
  margin-left: 25.41667%;
  margin-right: -100%;
  clear: none;
}
.solutionThumbnails li:nth-child(4n + 3) {
  margin-left: 50.41667%;
  margin-right: -100%;
  clear: none;
}
.solutionThumbnails li:nth-child(4n + 4) {
  margin-left: 75.41667%;
  margin-right: -100%;
  clear: none;
}

SassMeister-rendered.html

<ul class="solutionThumbnails">
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
</ul>