Kill 5 guards with a scaffold after they have been stunned by caltrops. (20 G)

In order to gain this achievement you must first have a caltrop bomb. You can buy these from the Black Market Dealers or by crafting them yourself. When they explode, they have spikes fly out and the guards that walk on them will hop up and down on one foot in pain.

After obtaining the bombs, go ahead and look for a scaffold. They are in many areas and are basically wooden planks/platform structures that help people do work. Normally they do not have anyone on them. If you run next to one holding RT , you will notice it says "Pull Down" as you run by. You will have to be running and holding the button to see it say that, then press B to execute the pull down. It will topple over. I suggest trying it once first before doing it with guards. These do not have to be at once, you could do it one at a time if you really wanted. Get the attention of a group of guards and bring them to the scaffold. Quick throw the bomb with Y (must be selected via RB menu) and the guards will walk on the spikes and start hopping up and down. Now run by the scaffold and press B to pull it.