Moving the non-working bobbins to either side helps visitors see the work in progress. Sheila is also demonstrating that (as a general rule), she works with two pairs at a time. With good visibility, they can see how she does the Cross, Twist, Cross, Twist (or whatever sequence she was doing at that time), and then moves two bobbins to the side as she picks up the second pair to again lace with two pairs as she works across that section.