It was only yesterday that I cleaned the holes in the bed of my 1927 Singer 99K and attached the seam guide for the first time. I had forgotten that I had never been able to get the screw in because the hole was gummed up. Having had good results with paraffin when cleaning up a Naumann machine with a stuck foot, I decided to try the same method to clean out the holes. I twisted the ends of a very narrow strip of cotton material and poked them up through the bed of the machine from below. Underneath, in the base of the machine, I put a little ramekin with a tiny amount of paraffin in it. Once the machine was lowered back into the base, the cotton strip was left lying in the paraffin. It acted as a wick, soaking up the paraffin and breaking down the residue that was gumming up the screw thread. I left the cotton strip in place for a few hours. Then, after removing the strip, I dipped an interdental toothbrush in paraffin and thoroughly cleaned the inside of the hole. It only took a few minutes, and then I was able to get the screw in. Success! Now I can use this machine with the seam guide. And I even remembered to take the ramekin out of the base.