The Solderer has been removed in version 1.6.x and higher and is replaced with the Processor Binding.
The Solderer is a device that is used to craft several items and blocks.
The Solderer is not sided. You can insert from any side and it'll automatically put the items in the right slot.
Use of JEI (Just Enough Items) is (highly) recommended to see the recipes of the Solderer.