I have many SAKs and other multitool knives. I have modded some of my knives. Here's an example of a Swiss Champ to which I added a lock-picking tool. To make such a modification I first pry off the Cellidor scale after soaking the knife in hot water for a minute. That way the press-fit scale is usually reusable. Replacement scales are not expensive, though. I always have several sets of spare scales at hand because I like to fit new scales every couple of years. I remove material on the bottom side of the scale to create storage space and an access port. In this case, I gave the tension wrench a slight bend and the resulting friction holds both tools firmly in place inside the handle. Other things you can fit inside the scale are micro SD cards, an RFID chip, a few meters of fishing line or sutures, a magnesium or ferrocerium firestarter rod, sewing needles, etc.
