Use the hinge for angles and the screen edges as rulers
Does Fold Protractor: Angle Finder work on iPhone Duo?
Yes, the developer says so: open, the Duo works as a bevel gauge that reads the hinge angle; closed, it works as a level, with rulers along the edges.
- App Store confirmedSpecial Glasses LLC, the developer, in the App Store description for version 1.0 (released October 15, 2026), which says the open Duo reads the hinge angle like a bevel gauge, and that a folded Duo works as a level.
Adapted for the fold
- Closed · Outer display
A level when closed
Closed, it works as a level: stand the phone on an edge to read its rotation, or lay it flat to see the tilt with a bubble. Rulers run down both long edges.
- Open · Inner display
A bevel gauge when open
Open and set into a corner or against two edges, it shows the hinge angle in big numbers, with rulers along the long edges of the inner display.
About Fold Protractor: Angle Finder
Fold Protractor turns the open Duo into a bevel gauge: set it into a corner or against two edges and read the hinge angle. The developer warns that readings and ruler marks vary with the phone and case. Closed, and on any other iPhone, it works as a level.
Evidence reviews
What we checked, when, and what the evidence establishes. Each record preserves the support label at that check.
· App Store page reviewed
App Store confirmed · iphone-duo
The App Store description mentions iPhone Duo: "Fold Protractor turns iPhone Duo into a bevel gauge." (version 1.0, released October 15, 2026).
App version: 1.0.
Store text only: we haven't seen the app running, and the store page doesn't show how each pose is used.
View reviewed evidence ↗
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Every iPhone app opens on iPhone Duo, but only updated ones fill the inner display. What an app looks like before its developer adapts it, how to tell which are ready, and which popular apps have said so.
Is this your app?
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Sources: Fold Protractor: Angle Finder on the App Store (apps.apple.com)
More for iPhone Duo
KeepCount
Tyler Hillsman / 1881 Digital, LLC
A board of tally counters: half-folded, counts sit above the fold and the buttons below
Simulator verified: Tyler Hillsman, the developer, in a submission to FoldHunt on October 17, 2026, with an unframed screenshot of the app in the iPhone Duo simulator in the press kit (keepcount.app). The App Store seller is 1881 Digital, LLC. The release notes for version 1.8 (released October 12, 2026) say KeepCount now adapts to the iPhone Duo's inner and outer displays, with a tabletop layout when it's partly folded.
- Book
- Closed
- Open
Calc Pro - The Best Calculator
Panoramic Software Inc.
Ten calculators and converters, with the tape of results beside the calculator when open
Simulator verified: Panoramic Software Inc., the developer, in a submission to FoldHunt on October 18, 2026, and in the App Store release notes for version 7.0.6 (released October 12, 2026), which describe the closed and open layouts. The app's page on the developer's website has pictures of both on the iPhone Duo.
- Closed
- Open
Sticky Widgets
Tyler Hillsman / 1881 Digital, LLC
Sticky notes as widgets, with a larger library and side-by-side editing on the Duo
Simulator verified: Tyler Hillsman, the developer, in the App Store release notes for version 5.4.0 (released October 13, 2026), which add iPhone Duo support with a larger library and side-by-side editing, and in a submission to FoldHunt on October 17, 2026, with an unframed screenshot of the app in the iPhone Duo simulator in the press kit (stickywidgets.app). The App Store seller is 1881 Digital, LLC; the App Store pictures show ordinary iPhones and iPads.
- Open