A private drive is meant to be just that -- private. However, when people see a driveway they take it as an open invitation to come on to the property. Laying a chain to block the driveway will keep most vehicles out and give the property its privacy. Any fence can be scaled, and any chain can be cut so this will not guarantee that no one will ever come in, but it will keep out the merely curious and those using the drive to turn around in.
Drill four holes around the circumference of the the coffee can, equal distance from one another and half way between the top and bottom.
Center a post in the coffee can. Reach through the holes from the outside with a marker and mark a dot where it lines up with the hole.
Drill 1-inch deep holes in the four sides of the post at the dot, so that when the post is set back into the coffee can the post holes line up on each side with the coffee can hole..
Drive a nail from the outside of the coffee can 2 inches deep into the post, using the holes as a guide. Do the other three sides the same.
Repeat the process with the other post and coffee can.
Pour the concrete into a wheelbarrow or other mixing container. Mix the concrete according to package directions.
Stand the coffee cans up and begin filling them with concrete around the post. Use a trowel or other thin tool to work the mixture past the nails and into the bottom. Stop every few inches of filling and tamp down the concrete by lifting the can and shaking it. You want to avoid air bubbles in the concrete.
Dry the concrete for several days.
Drill a hole the diameter of the eye bolt 6 inches from the top of the post and centered on one side. The hole should extend to the other side.
Slide an eye bolt through the hole and out the other side. The eye bolt can either be horizontal or vertical. Thread a nut onto the bolt and tightly up against the wood.
Cut the excess bolt off behind the nut with the hacksaw, leaving just 1/4 inch of bolt past the nut.
Peen around the edges of the end of the bolt with the round end of the hammer, forcing the bolt metal to deform and spread out. Hammer the spread out metal close to the nut, locking the nut into place and preventing it from being removed.
Dig a hole on each side of the driveway where you want the chain to go. The depth should be the same as the coffee can height, and the diameter should allow the can and nails to set easily down into it.
Set the concrete filled cans into the hole, with the eye bolts facing each other across the drive.
Fill the holes with dirt and tamp down until it is well packed around the nails and coffee can.
Slide the chain through an eye bolt and lock it to itself with one of the locks. Stretch the chain across the driveway to the other post and do the same at that end.
Screw reflectors onto all the the sides of the posts and hang a reflective "No Trespassing" sign in the middle of the chain on both sides.