Bresser T-Rex Instruction Manual page 46

Extruder
Double-click the Extruder icon to select the left and/or right extruder for
printing.
Supports
Because 3D printing is an additive process, each layer of filament needs a base
to be built on. The printer can gradually increase the layer size, as long as the
overhang angle is less than about 45 degrees. Otherwise, you need to create
support elements to serve as the base for adding additional layers. To edit the
supports, click the Edit menu, then select the Supports entry. Alternatively,
click the Supports icon. Click the Back button when finished editing the
supports.
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