# Ruler *Applies to: iOS, iPadOS · Updated 2026-08-13* Draw straight lines, circles, and perspective guides with Flow's Ruler, and position, lock, and snap it as you work. [Original article](https://bonobolabs.com/support/flow/ruler/) [Image: Flow Ruler] The ruler in Flow comes in two modes. The **simple ruler** places a ruler object on the page that you drag around and draw along, much like a real ruler. The **drafting ruler** is a powerful set of guides for everything from precise lines and circles to sophisticated perspective drawings. If you want Flow to tidy up shapes you have already drawn rather than guide you as you draw them, see [Lines and Shapes](/support/flow/creating-with-flow/lines-and-shapes/). ## Turning on the ruler Tap the ruler from the toolbar to turn it on. The ruler can be on while you use any drawing tool. You can also configure gestures to quickly access the ruler (see [Drawing and Gestures](/support/flow/managing-your-documents/preferences/#drawing-and-gestures)). Tapping somewhere on the page well away from the ruler turns it off again. ## Choosing a ruler mode [Image: Flow's ruler panel, showing the mode, magnet and reset controls] Turning the ruler on brings up the ruler panel. You can drag the panel by its grip and place it wherever suits you. The two buttons along the top switch between the **simple ruler** (left) and the **drafting ruler** (right). The selected mode is highlighted. In simple mode the panel stays compact, with just two more controls: - The **magnet** button snaps rotation to 5º increments - The **reset** button returns the ruler to its default position and rotation Switching to the drafting ruler grows the panel to add its own controls. Those are covered under [Drafting ruler](#drafting-ruler). ## Simple ruler [Image: Drawing along the edge of Flow's simple ruler] The simple ruler puts a ruler object on the page. Draw along either of its long edges and your stroke follows the edge exactly. ### Moving and rotating - **Press and drag** anywhere on the ruler to move it around - **Pinch** the ruler to change its size - **Rotate** it with two fingers, or grab the circular hole with Apple Pencil and turn Tap the magnet button on the ruler panel to make rotation snap to 5º increments as you turn. The circular hole is also a quick way to set the angle without dragging: - **Tap** it to rotate the ruler in 90º increments - **Double tap** it to set the rotation back to 0º ### Resetting the simple ruler Tap the reset button on the ruler panel to return the ruler to its default position and rotation. ## Drafting ruler The drafting ruler is the full drafting system, with guides, masking, snapping and perspective. [Image: Flow's ruler panel in drafting mode] Choosing the drafting ruler grows the panel to add three more controls: - **Shape** sets what you are drawing along: a line, a rectangle or a circle - **Mask** sets whether strokes are blocked inside or outside the shape - **Perspective** adds vanishing points for projected drawing Each of these opens a more detailed submenu when you tap it, holding the variations described in the sections below. The magnet and reset buttons stay where they were. ### Drawing with the drafting ruler - Blue lines indicate that your tool will lock to them when you draw - Grey lines are for reference, meaning your tool will not lock to them - Shaded areas are masked, which means drawing is blocked in these areas (see [Masking](#masking)). ### Positioning the Ruler [Watch video on Vimeo](https://vimeo.com/513631941) The ruler is placed on your document, so it stays the same relative to your drawing as you pan around. It also means you can zoom in and adjust the ruler with precision. The ruler has two main parts that you can move called _handles_. #### Position handle Moving this handle positions the whole ruler tool on the document. When you move this handle, the angle of your ruler doesn’t change - this lets you translate a set of parallel lines, or duplicate a rectangle and circle to a different location but retain the exact same proportions. #### Angle handle By moving the angle handle you can define a line at any angle, a rectangle of any proportion and a circle of any radius. ### Locking the ruler [Watch video on Vimeo](https://vimeo.com/513633198) Double tap the position handle to temporarily lock the ruler and prevent it from being adjusted. This is so you can start drawing a line from the origin point, without accidentally moving the ruler itself. ### Resetting the Ruler [Watch video on Vimeo](https://vimeo.com/513631605) Tap the reset button to re-position the ruler back into the centre of your current document position and return handles to their default layout. The default line angle is 45º. You can also double-tap the angle handle with your Apple Pencil to cycle between 90º, 45º and 0º. If you have Line with Single Guide enabled, tapping its handle will reset it to be 45º from the main line. Perspective guidelines are reset separately (see [Reset Perspective Guides](#reset-perspective-guides)). ### Snapping #### Without background pattern [Watch video on Vimeo](https://vimeo.com/513631196) By toggling the Snap button, you can choose to make the ruler automatically adjust the position of the angle handle when you move it so that the angle is set to precise 5º increments. When you move the position handle, it will intelligently snap along the horizontal and vertical axes as indicated by a yellow guide line. #### With dot grid, grid and isometric background patterns [Watch video on Vimeo](https://vimeo.com/513631410) Both the position and angle handles will snap to the background pattern intersection points. ### Lines Select Line mode and your tools will lock to the blue ruler lines when drawing. You will still see grey reference lines for rectangle and circle options. Tapping the Line button a second time allows selecting alternative line modes: #### Line with Single Guide [Watch video on Vimeo](https://vimeo.com/513633028) A second guide line appears offset from the main ruler line, at any angle you set by moving the handle. #### Line with Reflected Guide [Watch video on Vimeo](https://vimeo.com/513632667) Two additional guide lines appear offset from the main ruler line. The guide lines are reflected so when you adjust the angle handle, both lines will match but on opposite sides of the main ruler line. ### Rectangles and Squares [Watch video on Vimeo](https://vimeo.com/513631758) Select Rectangle mode to draw rectangles. For drawing perfect squares, turn on both [Snapping](#snapping) and the dot or grid [Background Pattern](/support/flow/documents/#background-options) #### Quadrilaterals Choose quadrilateral mode by tapping a second time on the rectangle menu button and selecting it. Drawing a quadrilateral allows you to position any of the four corners individually. - The position handle moves the entire shape around and is the origin. - The angle handle rotates the shape around the origin and determines overall scale. Double tapping it resets it to 45º from the position handle. - The other two corner handles can be positioned independently, double tapping them resets their angle to 0º and 90º respectively from the origin ### Circles and Ellipses [Watch video on Vimeo](https://vimeo.com/513632829) Select Circle mode for drawing circles and ellipses. When ellipse mode is active, a third handle appears. Dragging this handle changes the circle into an ellipse. You can reset this by double tapping the elliptical handle with Apple Pencil or by dragging the handle outwards to the maximum. ### Masking #### Draw on the edge In this mode, your lines are automatically locked to the ruler edges, indicated by blue lines, and no area is masked. #### Draw inside the edge Your strokes will only apply inside the shape and not in the darkened areas outside of it. If you have Line mode selected, one side of the line will be darkened and prevent strokes being made in this area. #### Draw outside the edge The inverse of the Draw inside the edge option, the opposite area appears dark and prevents strokes. #### Example: Masking shapes [Watch video on Vimeo](https://vimeo.com/513632111) #### Example: Masking lines [Watch video on Vimeo](https://vimeo.com/513632525) #### Example: Masking lines with guides [Watch video on Vimeo](https://vimeo.com/513632298) ### Perspective Turning on perspective mode adds vanishing points to allow advanced drawing with projection. Choose the number of vanishing points from the menu by tapping on the number. Your perspective guide remembers its most recent layout on each document you use it on. #### One point perspective [Watch video on Vimeo](https://vimeo.com/513171071) Shows a vertical, horizontal and single vanishing point which can be dragged to any position. #### Two point perspective [Watch video on Vimeo](https://vimeo.com/513630338) Two vanishing points appear with lines to them from the position handle as well as a vertical line. Each vanishing point can be independently adjusted horizontally. Vertical adjustment automatically applies to both vanishing points. #### Three point perspective [Watch video on Vimeo](https://vimeo.com/513630747) The third vanishing point is controlled a little differently. Commonly the third vanishing point needs to be positioned quite far from the drawing itself, so adjusting the vertical position is done by tapping on the ‘center’ indicator from the horizontal guide line and moving the slider. This allows controlling the position of the vanishing point when it is far off-screen. #### Reset Perspective Guides Tap _Reset Perspective Guides_ to reset vanishing points to default positions.