> ## Documentation Index > Fetch the complete documentation index at: https://docs.loft.build/llms.txt > Use this file to discover all available pages before exploring further. # Reference plane ```loft theme={"theme":{"light":"github-light","dark":"github-dark"},"languages":{"custom":["/languages/loft.json","/languages/loft-fragment.json"]}} refplane RP0 bearing 23deg at 50' ``` A reference plane is a datum you name so you can measure to it and build on it. `refplane.` goes wherever `grid.` does. It takes one of six forms: * **Plumb, at a station:** `refplane RP0 bearing 23deg at 50'` * **Plumb, through a point:** `refplane RV bearing 23deg at (grid.A, grid.1)` * **Flat:** `refplane USDECK elev level.L3 - 1'-6"` * **Tipped:** `refplane BW bearing 0deg tilt 1:12 at (grid.A, grid.1, level.L1)` * **Through three points:** `refplane RP2 through (grid.B, grid.2, level.L1) (grid.B, grid.3, level.L1) (grid.A, grid.2, level.L2)` * **A hinge**, turned about the line where a plumb plane meets a flat one: `refplane HG through (grid.B, level.L2) tilt 1:12` A tipped plane takes one of four words, the way the trades say it: a battered wall **tilts** (its top goes to the right of the bearing), a raked column **leans** (its top goes the way the bearing points), a roof **slopes** (it falls the way the bearing points) and a ramp **rises** (it climbs the way the bearing points). The angle runs strictly between `0deg` and `90deg`, and a rise over run is the same angle: `1:12` prints `4.764deg`. A tipped plane is placed at a point with three terms, the third a level or `z`. Four reference planes at bearing 0deg, the bearing pointing north, each tipped 20deg by its word: with tilt the plane stands along the bearing and its top goes to the right, east; with lean it stands square to the bearing and its top goes north; with slope it lies flat and falls north; with rise it lies flat and climbs north

Four reference planes at bearing 0deg, the bearing pointing north, each tipped 20deg by its word: with tilt the plane stands along the bearing and its top goes to the right, east; with lean it stands square to the bearing and its top goes north; with slope it lies flat and falls north; with rise it lies flat and climbs north

`lean` and `tilt` name one plane from bearings 90deg apart: `bearing 0deg lean 20deg` is `bearing 270deg tilt 20deg`. `rise` and `slope` name one plane from opposite bearings: `bearing 0deg rise 20deg` is `bearing 180deg slope 20deg`. `refplane.BW + 4'` is 4 feet toward the side the top leans to. Off a flat, sloped or rising plane, `+ 4'` is above it; off a plumb plane, it is to the right of the bearing, as a grid's station counts. A wall runs along, stops at or is held off a plumb reference plane only. A reference plane is included in the compiled output but isn't drawn by default; loft applications, including the loft app, can choose to display it. ## Parameters | Word | Accepts | Required | Meaning | | - | - | - | - | | `bearing`
`bearing 23deg` | angle | instance · one of: `bearing` · `through` · `elev` | the compass bearing the plane's line runs at, clockwise from project north — alone, a vertical plane whose station counts to the right of the line; with an angle word, the line it tips about | | `through`
`through (grid.B, grid.2, level.L1) (grid.B, grid.3, level.L1) (grid.A, grid.2, level.L2)` | line (direction z) | instance · one of: `bearing` · `through` · `elev` | three points the plane passes through, three terms each — the surveyor's three shots, the front the side they read counter-clockwise from — or, followed by `tilt`, a hinge: a vertical plane and a flat one, the line the plane tilts about | | `tilt`
`tilt 1:12` | angle | instance · optional | a wall tipped from plumb, its top going right of the bearing — a battered wall; between 0deg and 90deg | | `lean`
`lean 1:12` | angle | instance · optional | a wall tipped from plumb, its top going the way the bearing runs — a raked column; between 0deg and 90deg | | `slope`
`slope 4:12` | angle | instance · optional | a floor tipped from level, falling the way the bearing runs — a roof draining; between 0deg and 90deg | | `rise`
`rise 1:12` | angle | instance · optional | a floor tipped from level, rising the way the bearing runs — a ramp; between 0deg and 90deg | | `at`
`at 50'` | plane (parallel to this datum) or line (direction z) | instance · optional | with `bearing`, and only with it: a vertical plane's station along its own normal — a length, or a parallel datum plus a length — or a point the plane passes through, two vertical planes or three terms; a tipped plane takes three | | `elev`
`elev 22'-6"` | plane (normal z) | instance · one of: `bearing` · `through` · `elev` | a flat plane's elevation, as a level's | ### Reserved | Word | Rung | Meaning | Arrives with | | - | - | - | - | | `label` | instance | what the tag prints when it is not the id | a bubble or tag printing text other than the id — the grid's bubble is the one that ships | | `origin` | instance | the frame's origin — a point on the plane | the sketch grammar — a plane's frame written as a block: an origin and two directions on the plane | | `x` | instance | the frame's first direction, along the plane | the sketch grammar — a plane's frame written as a block: an origin and two directions on the plane | | `y` | instance | the frame's second direction, up the plane | the sketch grammar — a plane's frame written as a block: an origin and two directions on the plane | | `normal` | instance | the frame's third direction, out of the plane's front | the sketch grammar — a plane's frame written as a block: an origin and two directions on the plane | ## Datums | Datum | Shape | Status | Resolution | Rule | | - | - | - | - | - | | *(the plane)* | plane | core | intrinsic | The plane itself — a declared datum, no selection — referenced as `refplane.` wherever a grid can be: `(grid.A, refplane.R1)`, `along refplane.RP0`, `to refplane.RP0`, `past refplane.RP0`. Its front is the side its normal points to: `refplane.RP0 + 4'` is 4 ft in front of it. | ## Roles Never printed: a reference plane shows on screen as a guide, never on paper. This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.