This little trick will help keep your projects hooped securely and it costs mere pennies!
Some embroiderers use straight pins, but the secret weapon is a simple T-pin. Personally, I like the 1.5-inch size.
Insert the pin through both layers of fabric and stabilizer on top, against the hoop, right where they come out of the hoop. Then, insert the pin along the top edge of the hoop, parallel to the hoop edge, to keep layers tight and flat.
Pin around the hoop edge as necessary.
Where this is really handy is with larger hoops. The bigger the hoop, the more lose that the sides can become. T-pins keep stabilizer and fabric from shifting.
I find it most useful when stitching in-the-hoop projects using a fabric-type water-soluble stabilizer, particularly if the project is not finished in one sitting. Even when snug, the WSS can relax in the hoop. That can cause issues with registration and puckering.
To make pinning even easier, the DIME Hoop Mat keeps the hoop from sliding around.