Blocks are available in varying widths — ⅞", 1", 1-¼", and 1-½" — to accommodate a wide range of workpiece geometries.

Each block has an offset mounting hole: one face is ½" from the bolt center, while the opposite face provides a different offset depending on the block width. This allows each block to be flipped end-for-end to achieve half-inch positioning increments using the grid as a reference.

Example: With a 1-¼" wide block, one face sits ½" from the bolt center and the other sits ¾" from center. This means the same block can position a workpiece face at either a full-inch grid line or a half-inch point between grid lines, simply by flipping it around.

Blocks come in two types: clamping blocks (drilled and tapped to accept a fastener for securing the workpiece) and backstop blocks (plain faces used only as positioning references with no threaded hole).

Positioning Blocks

Positioning Blocks (Alternate View)

Change the fastener depending on clearance requirements:

• Hex Bolt (19mm / ¾"): The preferred option for speed and ease of use. A standard wrench allows rapid tightening during setup and workpiece changes. The block's offset hole is specifically designed to provide clearance for the hex head — always orient the block so the threaded hole is farther from the working surface.
• Socket Head Cap Screw: Provides a lower profile where vertical clearance above the block is limited.
• Set Screw: The most compact option for tight-clearance situations where any bolt head protrusion would interfere with the workpiece or its rotation path.

4" × 6" Rectangular Tubing: Position backstop blocks at 2" from center on the 4" sides (4 ÷ 2 = 2) and 3" from center on the 6" sides (6 ÷ 2 = 3), aligning block edges directly on the corresponding grid lines. On the clamping side, a ⅞" block provides an intentional ⅛" extra clearance to accommodate weld seam bulge — a common characteristic of welded tubing that prevents it from sitting perfectly flush. This block can also be flipped and used as a conventional ½" offset block for even-inch dimensions.

1-½" Angle Iron: Using 1-¼" wide blocks with the ¾" offset facing the center of the jig plate positions the backstop faces exactly ¾" from center (1-½" ÷ 2 = ¾"). A standard block on the outside provides the clamping point, and a spare block can be used as a spacer between the hex bolt and workpiece to prevent marring.

3" Rectangular Tubing: Position blocks with the offset flipped so the working edge falls at the 1-½" mark — the center of a 1" grid square (3 ÷ 2 = 1-½"). This demonstrates how flipping blocks provides precise half-inch positioning increments. An inside clamping block with a threaded fastener secures the workpiece against the backstop blocks.