Some of the most interesting camera trap sets are between rocks and hard places.
We're talking about caves, mine shafts, lava tubes, natural chimneys, boulder piles, rock recesses, crevices, fissures and other situations you commonly encounter around bluffs and rimrock.
The camera trapper's usual tools of the trade, like bunji cords, rope, wire, and stakes with special mounts usually don't do the trick where trees are absent and the ground is solid rock or sandstone. `
So you make a cairn or prop the cam between rocks like I did at the Wind River Ranch last year.
A good wind can move it, and a bear can topple it.
The ideal tool is an expansion post, but it took neighbor Richard and me a few weeks of desultory discussions about the relative merits of compression springs versus threaded rods before we had a plan.
We settled on half inch threaded rod as the means of expanding and locking the post in place.
This is basically the principle of the car jack.
The posts were made from pieces of used conduit (7/8ths inch outside diameter) cut to various lengths.
We drove nuts into both ends of the posts, and screwed short lengths of threaded rod into one end.
Several sections of expansion post measuring 36, 18, and 9 inches.
The middle piece is 2 sections screwed together.
Then we braised the nuts and rods into place.
Any number of lengths can be screwed together to fit gaps of different size.
The end pieces are the key parts for fixing the post solidly in place.
A short stationary end piece is flattened like a chisel. It locks into place as you turn the screw by hand.
The turning end is rounded (a carriage bolt head) or pointed (a lag bolt or a threaded screw machined to a point) and thus can be turned on a 12-inch length of threaded rod.
It bores into a crevice or an irregularity in the rock.
We tried it out at the rock recess, and it worked like a charm.
The post is solidly in place with no wiggle room.