: Often called a standard or flat-blade screwdriver, it features a single chisel-shaped tip designed to fit into a straight slot on a screw head. It is the oldest and simplest type of screw drive.

In the world of mechanical assembly and maintenance, these two screwdriver types remain the most fundamental:

: On equipment like the 6800 Series Single Column Table Model, page or section 121 details testing limit stops, a task requiring minimal tools to ensure the crosshead moves safely.

The phrase appears to be a direct instruction or requirement from a technical manual or assembly guide, likely for an Instron testing system. In such contexts, "121" often refers to a specific procedure or page, such as testing limit stops or general maintenance, where these two tools are the only ones required. The Two Essential Driving Tools

: Distinguished by its "X" or plus-shaped tip, it is designed for Phillips screws. This design is self-centering, which prevents the driver from wobbling and reduces the risk of slipping sideways compared to slotted screws. Contextual Usage in Maintenance

Phillips and Pozidriv cross-head screws – explained in simple terms

When a manual specifies using only these two tools, it typically implies a "tool-free" or "basic-tool" maintenance philosophy intended for the operator rather than a specialized technician. For example:

: Many mass-produced items use these two drives for user-accessible parts, while reserving more complex drives like Torx or Hex for internal components to discourage unauthorized dismantling. Best Practices for the Task