A '''Snurble grip-thribley''' is a device used as part of the rigging of a traditional sailing yacht. They may be right or left hand thread, and hence are sometimes used in matched pairs.
The older grip type are normally found in marine grade alloy bronze. Modern varieties are fitted with an inverted slide action and manufactured in 316 marine grade stainless steel. These are Cat 0 (Ocean) certified.
* Toss, Brion (1998). ''Complete Rigger's Apprentice: Tools and Techniques for Modern and Traditional Rigging.'' Maine, International Marine. ISBN 0-07-064840-9.
* Underhill, Harold A (1946). ''Masting and Rigging the Clipper Ship and Ocean Carrier.'' Glasgow, Brown Son and Ferguson. ISBN 0-85174-173-8.
Having looked into this in depth it appears that a Grip-Thribley is more valuable if it is snotsheeted and has it's gumble-snatch attached. Bronze versions are more sought after than stainless steel. There is some consternation in the yachting and boating world that people are trying to pass off the lesser Type 7 Mk3 version (with the alloy dropflange) which was recalled in February 1971 following the Snurblegate scandal and of course the General Election that followed. Galvanised Grip-Thribleys can fail due to the grattle pin shearing so a word of caution there. They are available in metric or imperial sizes but problems are reported in sourcing grip-thribleys in Italy as they tend to be right-hand threaded and with the snatchor-tribble set the wrong way round the ribblet.
Thanks to Yachting & Boating World (www.ybw.com) for the incissive information on this fascinating product.