Screen missing from opening to crawl space?

Question

We have a small house behind the main house. Ventilation to its crawl space is through cinder blocks placed on their sides. The screen on one of them seems to have fallen off (see attached photos). What can I do to replace it? Plans to the back house show a scuttle to the crawl space, but I haven't been able to find it--I'd have to pull up the carpet in order to access it, if it's there.

http://farm4.static.flickr.com/3088/2690871104_f5a362a35c_m.jpg

http://farm4.static.flickr.com/3016/2690058607_8ed299856a_m.jpg

http://farm4.static.flickr.com/3004/2690870710_3d01284f31_m.jpg

Answer 1

i hate to say the obvious but check and see (when u get under there) how the other screen are attached id say the easiest way would be to attach a small wood frame around the opening underneath the house using concrete anchors and liquid nail and staple the screen to the wood