When building concrete forms there's sometimes existing concrete that's adjacent to which you can anchor. If so, and you need to fasten a cleat to back your form, here's a quick method. You'll probably be have a number of locations where you'll need these fasteners, so you can start by cutting a bunch of pieces of tie wire about 5'' long. Put the material to be fastened in place, let's assume it's a 2 x 4, drill through it and into the concrete with a hammerdrill using a 5/32'' masonry bit. The hole should be deep enough to accommodate the 16d duplex nail that you'll be using plus a little extra depth to make this go quickly. Insert a piece of tie wire through the 2 x 4 until it bottoms out in the concrete. You can then fold the extra tie wire off to the side and drive your nail home. When your ready to strip your forms you'll find removing these fasteners easier than if they were form spikes.