This upright wooden beam bears the load of the roof support system in an underground heading. Placed on either side of the tunnel, straddles hold up the horizontal cap piece to form a complete timber set. They transfer the immense vertical pressure from the rock mass above down to the floor or sill.
Check the straddle on the left side of set four, it looks like it's starting to take too much weight.
A bowing straddle is an immediate warning sign that the roof pressure is exceeding the timber's compressive strength.
Related terms
Studdle
A vertical or inclined timber prop used to support a platform or separate shaft compartments.
Stull
A heavy timber prop wedged between the hanging wall and footwall of a stope.
Lath
A heavy plank driven ahead of a tunnel face to support loose ground during excavation.
Timberman
A skilled underground worker responsible for cutting, fitting, and installing wooden structural supports.