These keyline shapes include:
- vertical rectangle
- horizontal rectangle.
I did not find any downloadable resources of the keyline shapes to base the creation of new Android icons, so I created my own template in SVG format, at 4 times 48 pixels size, i.e. 192 pixels. The template looks as shown in the screenshot of Inkscape below.
Each keyline shape is placed on a separate layer.
Simply toggle on the desired keyline shape e.g. Horizontal rectangle in order to use it as a guide in creating new icons.
The SVG template can be downloaded from this site https://www.dropbox.com/s/3fhijfrf3zipnjm/mat_dgn_icon_template.svg?dl=0 if you want to use it.