Honestly, the most reliable way is to bolt it down with concrete anchors—not just regular screws, because those can loosen or be pulled out pretty easily. Here’s the method I use.
First, choose the right anchor for your bench. If the legs have mounting holes and your concrete slab is solid, 3/8-inch or 1/2-inch wedge anchors are perfect. For lighter benches or smaller holes, Tapcon concrete screws can work, but they’re not as theft-resistant. If you want maximum security, use epoxy anchors: you set threaded rod into epoxy and bolt the bench down after it cures.
Next, set the bench exactly where you want it. Use a marker or a pencil to mark the holes through the bench legs. Move the bench away. Drill each hole with a hammer drill and a masonry bit that matches the anchor diameter. Drill about 1/4 inch deeper than the anchor needs. Clean the dust out of the hole with a vacuum or a squeeze bulb so the anchor grabs properly.
Now insert the anchor through the bench leg and into the hole. For wedge anchors, you’ll need to hammer the anchor down slightly so the sleeve expands, then tighten the nut until it’s snug. If the bench feet are thick, you may need longer anchors. Don’t over-tighten, or you can crack the concrete.
After it’s bolted down, make the hardware tamper-resistant. Use security Torx bolts, pin-in-Torx screws, or shear nuts. You can also fill the bolt heads with a dab of epoxy or concrete patch after tightening—this makes it much slower for a thief to unbolt. If your bench has no mounting holes, drill through the legs or attach heavy-duty L-brackets to concrete and bolt the bench to them.
For extra peace of mind, run a hardened steel cable lock through the bench and around a solid anchor point. It’s not as clean-looking, but it stops the quick grab-and-run thefts.
One last tip: check your local code or HOA rules before drilling into a front porch or walkway, and if the concrete is thin or cracked, anchor into a deeper slab or add a steel base plate to spread the load.