Like a page node, member page, resource item page?
Code:
@media (min-width:@maxResponsiveWideWidth)
{
#XenForo .mainContainer
{
float: right;
margin-left: -{xen:calc '@sidebar.width + 10'}px;
margin-right: 0px;
width: 100%;
}
#XenForo .mainContent
{
margin-left: {xen:calc '@sidebar.width + 10'}px;
margin-right: 0px;
}
#XenForo .sidebar
{
float: left;
}
}
This would make your sidebar on the left for every page, you can add a class after the #XenForo to target specific pages, but knowing what you want it on would help