Solar garden lights are designed to be shoved into the dirt along a sidewalk path, like spikes. I wanted to illuminate the stairwell of my rock wall, at my Civil War-era farmhouse. This shows how I did it, with cheap, but bright Westinghouse solar lights - $4/each, at Wal-Mart.
Step 1: Remove the Rod on the Bottom
This is one of those $4 Westinghouse solar lights. You don't need the stake on the bottom, just the top part, which contains the solar cell, battery, light and lens. I had to doctor the picture below - basically remove the stake and save it for something else.
Step 2: Bend the Wire Into a Ring, With Legs
See the black line in the picture? That is some thick galvanized wire, ten inches long. You could also use thick copper wire, like home electrical wire, but really, crackheads will steal any copper they see, so why invite that? Plus, grey wire will blend in with concrete. This wire is the thickness of coat hanger wire, but you should use galvanized wire, so that it doesn't rust, like a coat hanger would. If it rusts, you might get rust stains going down your wall.
I bent the wire into a circle (a ring), a little wider than the clear plastic lens (tube) that surrounds the LED light, then out an inch on each side, and then bent a leg out, on each side. Then I just stuck the light's cylindrical clear lens inside the ring, with the legs sticking out to the side.
NOTE: Although the picture shows a perfect circle in the ring, I made the ring a litle more oval than a perfect circle, so that the lens would friction-fit (so it would stay tight) inside the ring.
Step 3: Insert Legs in Crack Between Rocks
See the legs? I stuck them inside a crack between the old rocks in the wall. I lifted the rock above it up, and stuck the legs under the rock, so that the leg would have some weight on top of them. That will keep the wind from blowing it out. Then I stuck it right up against the rock.
That's it! You are done! Do this for each light. I did four; two on each side.
Step 4: Right Side View
Here are the lights on the right side of the step. See, there was no place to drive the stakes into, anyway; it is just 100-year old rocks everywhere here.
Step 5: Left Side View
Here are the two lights on the left side of the step. You can also see the old wrought-iron gate to the left. The gate is just sitting there, leaning against the stairwell wall, because the hinge pins rusted out, but we don't care. It looks rustic, and we would never shut the gate anyway.
That's it - I just wanted to light up the steps - they are very crooked, and it is quite difficult to walk up them in the dark. I don't have a picture of the steps lit up in the dark - I forgot to take a picture after dark, but it is nice and bright.
Our farmhouse is ~143 years old, and I don't know how old the stairwell is - I have a picture of the house from 1911, which shows the steps. Anyway, the steps are at least 100 years old.