I fabricated the cam locking tool out of angle iron and bar stock cold rolled steel. The bar stock that inserts into the slots in the back of the cams bent and broke off the edges of the cam slots. That was after my third re-fabrication of the thing with progressively stronger steel. After that I gave up and bought a knock-off of the 999 5452 tool from Pro-Auto Tools on eBay. $310 with shipping -- it also includes the crank lock and cam cover lowering tools. It worked perfectly in allowing me to loosen the incredibly tight exhaust cam sprocket inner bolt. I figure it was worth the expense and wait, and probably I will be able to resell it later. This was the first special tool I have ever bought in many years of working on Volvos. Guess I'm just cheap.