Tapered round locks prevent sliding in all directions unlike top and side locks, which only prevent sliding in one direction. Install them where the two halves of the mold meet, often called the parting line. You’ll need to machine pockets in each half of your mold separately, so you’ll need to take extra care to make sure the two pockets are aligned. For a complete pair, you’ll need a male and female lock with matching ODs. The height does not need to match.