Introduction to Drawing Tools
There are two types of drawing tools in Snagit: tools that create objects and tools that directly edit your capture. Tools that create things like callouts, text, arrows, or stamps create an object that "floats" above your capture. These objects can be re-arranged, shuffled and manipulated without affecting your capture underneath. The Selection, Fill, and Eraser tools directly edit your capture.
Object tools include:
Callout
Arrow
Stamp
Pen
Highlight
Text
Line
Shape
Note: When an object is flattened, it becomes a part of the capture. Those objects can no longer be edited separately from the capture.
Direct edit tools include:
Selection
Fill
Eraser
Note: The Zoom tool is also in the Drawing Tools group, but doesn't actually edit your capture. You can also zoom using the slider on the lower right corner, or by holding <CTRL> and moving the mouse scroll wheel.
The Style Gallery
After you select a tool, select that tool's appearance from the style gallery. The gallery drops down to show you a variety of default styles for the selected tool. You can also customize the tool's settings using the Outline, Fill, and Effects dropdown menus.
Here's a brief overview of the Outline, Fill, and Effects menus.
Outline

Settings for the outline of a tool are located in the Outline menu. This is where you select how the outline for things like callouts and shapes look. For tools like the Arrow and Line, this is where the color, width, and style is selected. (Arrows and lines are considered "all outline.") For the Pen tool, the brush shape is selected under the Shape sub-menu.
There's a basic color palette to select a color for your tool; you can also use a more advanced color selector or select a color directly from your image.
Width is used to select how thick (or thin) lines appear. Select a width for your line, or use the Custom Width dialog to specify a pixel width.
Shape is used to select the shape of callouts and shapes as well as the brush style for the Pen and Eraser tools.
Dashes is used to select the line style for the Arrow, Line, and Shape tools. Select from a variety of dashes.
Ends is used to select square, rounded, or other ends to lines and arrows. You can also select the type of arrow-head used. Select from a default list or customize to your exact specifications.
Fill

For objects that have an inner color, the Fill menu selects this color. You can also use a more advanced color selector or select a color from your image.
Gradient is used to select the style of callouts. Choose from No Gradient, Shaded, or Glassy.
Tolerance is only used with the Fill tool. It controls how close the surrounding color being filled must match the original filled color in order for it to be replaced. A fill tolerance of zero means an exact color match. A tolerance level above zero matches similar colors. The higher the number, the less precise the match needs to be.

Effects

Shadow is used to give the selected object a drop shadow. Choose which direction the shadow is cast, or select More Shadows for custom shadow options.
When selected, Create as Vector creates drawing tools on the canvas as objects. Deselecting this means that all objects drawn on your capture become a part of the image and are not editable.
When selected, Antialias means that the edges of objects drawn on the capture are antialiased. Antialiasing is a technique that softens the edges of objects in order to make them appear smoother by using a slight color change between the object and the rest of the capture.
Unless you have a specific reason to turn Create as Vector or Antialias off, you should leave them on as they generally improve the quality of your finished capture.
The Opacity menu allows you to select an opacity level for the selected object or tool. Change the opacity level to change an object from appearing opaque to varying levels of transparency. Changing the opacity on an object does not require a file format that supports transparency, as the object is flattened after it is saved.

Mini Toolbar
In addition to using the Outline, Fill, and Effects menus to change the style of your drawing tools, you can use the Mini Toolbar. When you select an object drawn on the canvas, the Mini Toolbar fades in to view if you move your mouse towards it. You can also make the Mini Toolbar appear instantly by right-clicking on an object (it appears just above the context menu).

The Mini Toolbar gives you quick access to change most of the style settings for that object.
Tip: Save your customized styles in the gallery by adding them as quickstyles. These show up on the bottom of the styles gallery. To add a quick style to the gallery, right-click on an object and select Add to Quick Styles from the menu.

Callout
Arrow
Stamp
Pen
Highlight
Text
Line
Shape
Selection
Fill
Eraser