Channel locks are mechanical or computer settings that basically immobilize one set of wheels on your carriage. When applied, you can only roll the carriage up and down -or- left and right. You may be able to use small clamps from the hardware store. Take a look at your carriage & see if there's a place you can put them.
In theory, you could use them to SITD, but your quilt needs to be loaded perfectly straight on the frame and the seam needs to be sewn perfectly straight.
Don't understand your comment about pinning. If you are using a short or mid arm on a frame, you would only pin to attach the sandwich to the frame.