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Trapping malevolent or mischievous spirits with thread appears to be a worldwide practice. The spirits are believed to be fascinated by the threads, such that they become entangled in them. For serious magical protection, one should either bury or burn the threads once they have trapped unwanted entities. Nigel Pennick described burying them in a "Cambridgeshire Witch Bottle", having caught a sprite in them in a specially constructed trap (Pennick, 2005). He also describes the use of such glass bottles as apotropaic devices, stuffed with wool threads and sealed into lintels.
Hanging glass balls in windows appears to have become popular early in the 19th century. These balls were usually mirrored "witch balls", deflecting harmful influences, probably derived from the continental tradition of garden watch balls, that allowed intruders, etc., to be seen (Hewitt, 2018). Sometimes, however, as here, the ball would be of clear glass and stuffed with threads, combining the two traditions.
This ball from Suffolk contains silk threads and was clearly used, as the threads have faded, such that it is not now possible to be certain what colours were originally included. It would have had a metal hanger braced against the inside of the hole for suspension."