Thread gets picked up. Machines are covered when not in use. The Siamese has a habit of going "chomp" close to the spool on serger, so she would chomp on the PQ1500 spool also. The Pfaff will shut the top if using the horizontal spool, and if you take the vertical guide out and lay it down, she doesn't see the spool at all. You can also remove the spool and sit it in the spot for the horizontal spool and close the top of the machine. The vertical spool holder with guide is expensive and I don't want to replace it.