Some sheet metal designs (for example, transitional shapes created with Lofted Flange) created from closed profile sketches require a rip to flatten them.
A cut feature can also create such a gap, but the Rip feature has edges normal to the cut surface, and several options to simplify feature creation.
You can create rips in three ways:
A Single Point rip uses a single point on the edge of a surface. The selected point can be a midpoint on an edge, an endpoint on a face vertex, a work point, or a sketched point from a previously created sketch.

A Point-to-Point rip uses points on opposite sides of the face to define the Rip begin and end. The two points can be work points, midpoints on face edges, endpoints on face vertices, or sketch points from a previously created sketch.

A Face Extents rip removes any entire selected face (typically a bend face). You can also use a Face Extents Rip feature to remove a small bend face created as the result of a Lofted Flange created using Press Brake output.

You can place a Rip feature anywhere within the feature history. A single sheet metal model can contain multiple Rip features.
The labels that appear in the Rip dialog box depend on which type of rip you specify.
On the ribbon, click Sheet Metal tab
Modify panel
Rip
.
In the Rip dialog box, Rip Type drop-down list, specify how to create the rip.
Use Rip Face to select the face of the sheet metal model to rip.
For single point or point-to-point rip, do one of the following:
(Optional) For a single point rip or point-to point rip, in Rip Gap Value, enter a value that differs from GapSize.
(Optional) For a single point rip or point-to point rip, specify whether to locate the Rip gap on the selected point, or offset to the right or left.