Raphia is used to provide support to branches when they are being bent into proper position. Raphia is applied wet and will shrink when it dries providing a nice tight covering on the branch. Raphia helps keep the bark/branch from breaking.

Bjorn Bjorholm Rafia demo by BonsaiPoint  New 02-18-2018 Note: Really great video on using Rafia. 

raphia1, raphia 2, raphia 3, raphia 5, raphia 6, rapfia 7, raphia 8 , Wire/Bending/Branch Placement by Francios Gau   Nice set of video’s showing  you how Raphia is applied and used. Note: No video 4.