For making Bootstrap's pull classes be breakpoint-specific

pull.less

// Floating - like Bootstrap's pull-left/pullright classes, but breakpoint-specific
// Usage: .pull-right-sm, .pull-left-md etc.
.make-pull-left(@breakpoint) {
    .pull-left-@{breakpoint} {
        float: left !important;
    }
}
.make-pull-right(@breakpoint) {
    .pull-right-@{breakpoint} {
        float: right !important;
    }
}
.make-pull-none(@breakpoint) {
    .pull-none-@{breakpoint} {
        float: none !important;
    }
}

// Extra small grid
@media (min-width: 0px) and (max-width: @screen-xs-max) {
    .make-pull-left(xs);
    .make-pull-right(xs);
    .make-pull-none(xs);
}

// Small grid
@media (min-width: @screen-sm-min) and (max-width: @screen-sm-max) {
    .make-pull-left(sm);
    .make-pull-right(sm);
    .make-pull-none(sm);
}

// Medium grid
@media (min-width: @screen-md-min) and (max-width: @screen-md-max) {
    .make-pull-left(md);
    .make-pull-right(md);
    .make-pull-none(md);
}

// Large grid
@media (min-width: @screen-lg-min) {
    .make-pull-left(lg);
    .make-pull-right(lg);
    .make-pull-none(lg);
}