Halo Ruler render
Halo Ruler render
Halo Ruler render
Halo Ruler render
Halo Ruler render
Diagram from above: the ruler’s scale edge laid along the middle of a shaft, zero end against the base, the tip reading 5 1/2 inches right at the edge
Two views from above, the ruler’s scale edge along the middle of a shaft: bone-pressed, the zero end through the soft tissue to the bone, reads 6 in; non-bone-pressed, the zero end on the surface, reads 5 1/4 in
Halo Ruler render
Halo Ruler render
Halo Ruler render
Halo Ruler render
Halo Ruler render
Halo Ruler render
  1. Halo Ruler render
  2. Halo Ruler render
  3. Halo Ruler render
  4. Halo Ruler render
  5. Halo Ruler render
  6. Diagram from above: the ruler’s scale edge laid along the middle of a shaft, zero end against the base, the tip reading 5 1/2 inches right at the edge
  7. Two views from above, the ruler’s scale edge along the middle of a shaft: bone-pressed, the zero end through the soft tissue to the bone, reads 6 in; non-bone-pressed, the zero end on the surface, reads 5 1/4 in
  8. Halo Ruler render
  9. Halo Ruler render
  10. Halo Ruler render
  11. Halo Ruler render
  12. Halo Ruler render
  13. Halo Ruler render

Halo Ruler

$24.99

Designed for one measurement: bone-pressed length. The scale starts at 0 at the very tip, and the numbers run right along the edge that sits against the shaft, so you read the mark where you measure instead of across the ruler. Every corner is rounded, so the end you press in doesn’t bite.

Free with a TriPad pre-order. Pre-order a TriPad and get this ruler free, packed in the same box. It ships with the TriPad by late January 2027, not separately. Want it sooner? Buy it here on its own.

SKU: HX-BP1 Category:

Zero starts at the end

Most rulers waste the first few millimetres before the scale begins, which is exactly the part you need when you are measuring from the bone. On the Halo Ruler the scale starts at 0 at the very end of the ruler, with no blank margin. Press the end in until it seats, read at the tip, done. Nothing to estimate and nothing to subtract.

An end made for pressing — at both ends

A bone-pressed measurement means pushing the end of the ruler in firmly. A thin plastic edge bites, and how hard you press changes the number. Both ends of the Halo Ruler are broad faces with hard-rounded bottom and side edges that spread the load, so you can press confidently — and because there is a zero at each end, whichever way round you are holding it, the end you press is the end you measure from. The top edge stays crisp, because that is the edge you sight the zero along.

The numbers sit on the edge, against the shaft

Each scale’s ticks and numbers run right along its own long edge. Lay that edge against the shaft and the mark you read is right where you are measuring. Most rulers put a scale you have to read across the width of the ruler, 40 mm away with nothing to line up against; this one never asks you to.

Inches run from one end, centimetres from the other, and there is a zero at both ends. Turn the ruler round and the other unit is now on the edge against the shaft, zeroed at the base, with an end built for pressing there too.

Inches are graduated to 1/8, centimetres to 2.5 mm (quarter centimetres).

Black on white, not moulded in

The scales are a second colour, not a texture. They are printed onto the face in a second filament, standing a fraction proud of it, black on white — so you read them at a glance instead of tilting the ruler to catch the light on a groove. A continuous rail runs the length of each scale hard against its long edge — the edge line most rulers have — and every tick in that row meets it.

Rounded corners, nothing sharp

The four corners are rounded 5 mm in plan, the bottom and side edges carry a 1.2 mm roll, and both pressing ends are rolled harder still. Nothing you hold or press against is sharp. Only the top edges stay tight, at 0.4 mm, so the scale can start right at the zero.

How to measure

Consistency matters more than any single number. Use the same method every time.

Bone-pressed length (BPEL). Place the ruler along the top of the shaft with the zero for the unit you are reading at the base — inches and centimetres start at opposite ends, so turn the ruler round rather than trying to read the far edge. Press the end in until it stops against the pubic bone. Read where the tip falls. Press with the same firmness every time — this is the measurement most affected by technique, and the reason the ends of this ruler are shaped the way they are.

Non-bone-pressed length (NBPEL). The same measurement without pressing in. It reads shorter. Record which one you are taking; do not mix them between sessions.

Reading the mark. Sight straight down at the mark with your eye directly above it, not at an angle.

How often. Weekly or monthly beats daily. Normal variation between sessions is larger than any real change over a few days.

What’s in the box

  • Halo Ruler, 12 inches / 30 cm, white with black markings

Specifications

  • Length: 12 inches / 30.48 cm, with a zero at each end and no blank margin before either
  • Width: 1.57 in / 40 mm
  • Thickness: 0.157 in / 4 mm
  • Inch scale graduated to 1/8 in; centimetre scale graduated to 2.5 mm
  • Inches read from one end, centimetres from the other — a zero at each end
  • Both ends shaped and rounded for pressing
  • Both scales on a single face; the underside is blank
  • All edges and corners radiused
  • Two colours: white blade, black markings, printed as one part with no assembly. The markings stand 0.4 mm proud of the face
  • Material: PETG, chosen for heat resistance, so it holds its shape through shipping, a hot mailbox or a parked car far better than common printed plastics
  • Printed in the USA

Safety and care

  • Not a medical device. This is a measuring tool.
  • Adults 18+ only.
  • Clean with soap and warm water or an alcohol wipe, and let it dry. Do not put it in a dishwasher or leave it on a car dashboard in direct sun — that gets hotter than the plastic can take, and it can warp.
  • Keep BOTH ends undamaged. Each one is the reference surface for the scale that starts there, so a chip or a scuff on either is an error in every measurement taken from it. Replace the ruler rather than working around it.
  • Do not use on broken or irritated skin.
  • For hygiene reasons, we don’t accept returns once an order has shipped, opened or not, unless it arrives damaged or isn’t what you ordered. See our Refund and Returns Policy.

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