This thinset sticks like mastic?
There is more 'slide' while setting,with a thinset than a premixed mastic---some grip better than others-
Most setters will leave out the first (bottom) row of tiles and attach a temporary ledger board to give the tiles a firm starting point.
Once set the tile are more firmly attached with thinset---and there is no chance of the tiles coming loose in a wet area---bucket mastics will dissolve when exposed to water--
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