Yes it is canvas along the railings. As both Rondondo and travesty both mentioned USCG used them as water protection from wind n waves for guys on lookout originally USCG used white and later dark Blue from the late 1990s on most of their vessels and these were inherited to both The Philippines and Nigerian navys after they purchased them off the USCG in 2011. Though i do believe the Filipinos may have their white Canvas covers recently resprayed to grey or had grey ones made to replace the white ones.
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"The British Air Farce have droopped their bums on the water works..They have scored a direct hot on the pimps"- British agent/gendarme Officer Crabtree, "Allo,Allo."