I've constructed a nest of DIVs that make up a border between the header structure and the body (it will go in header.php of a WordPress blog that is based on Bootstrap 3). Reduced down to its basics, the 100x100px blocks always stay as 100px square blocks - when the available space is reduced to less than 100px, the blocks (that would normally overflow or be partially hidden) drop to the next line - which is hidden by an overflow:hidden declaration. Ultimately these little blocks will contain individual images which is why they cannot distort or partially overflow. So the code...
<div style="height:100px; width:100%; overflow: hidden;">
<div style="max-width:1600px; margin: 0 auto;">
<div style="width:50%; float:left;">
<div style="height:100px; width:100px; float:right; background-color:blue;"></div>
<div style="height:100px; width:100px; float:right; background-color:red;"></div>
<div style="height:100px; width:100px; float:right; background-color:blue;"></div>
<div style="height:100px; width:100px; float:right; background-color:red;"></div>
<div style="height:100px; width:100px; float:right; background-color:blue;"></div>
<div style="height:100px; width:100px; float:right; background-color:red;"></div>
<div style="height:100px; width:100px; float:right; background-color:blue;"></div>
<div style="height:100px; width:100px; float:right; background-color:red;"></div>
</div>
<div style="width:50%; float:right;">
<div style="height:100px; width:100px; float:left; background-color:red;"></div>
<div style="height:100px; width:100px; float:left; background-color:blue;"></div>
<div style="height:100px; width:100px; float:left; background-color:red;"></div>
<div style="height:100px; width:100px; float:left; background-color:blue;"></div>
<div style="height:100px; width:100px; float:left; background-color:red;"></div>
<div style="height:100px; width:100px; float:left; background-color:blue;"></div>
<div style="height:100px; width:100px; float:left; background-color:red;"></div>
<div style="height:100px; width:100px; float:left; background-color:blue;"></div>
</div>
</div>
</div>`
edit: There are two sets of images (the ones on the left 'look' center and the ones on the right are mirrored to also 'look' center. So it is the endmost Divs that disappear on both sides. Hence the convoluted nest. Note that reversing the lefts and rights means the blocks could also disaapear from the middle.
Now, so far as I understand, Bootstrap is designed to traverse down the various screen widths of devices in column 'steps'. Whereas my code steps down in 100 pixel steps from the largest to the smallest screen/browser sizes.
So although I've taught myself the Bootstrap '12 column' approach, I'm not sure how to mark my code up correctly for canonical Bootstrap CSS. That's why there are no IDs or Classes in my code yet, and everything is inline.
Are there any Bootstrap gurus out there that can guide me?