Using halftones is a graphic designing technique that uses dots of varying sizes, spacing and shades to simulate the appearance of various continuous tones and shades across an image. Halftone images are often used in stencilling and printmaking because the printing technique can use a single colour of ink to create the illusion of multiple shades. You can create halftone images for stencilling in graphics editing programs, such as Photoshop, or online with free programs such as The Rasterbator.
Open up the image you wish to create as a halftone stencil in a graphics editing program, such as Photoshop. If the image isn't already in black and white, convert it to grayscale by selecting "Image>Mode>Grayscale".
Open up the "Bitmap" option by selecting "Image>Mode>Bitmap". In the bitmap dialogue box, select the drop down menu under "Method" and select "Halftone Screen".
Set the number and size of the halftone dots by entering values in the "Output" text box. The output is defined in terms of pixels per inch, so fewer pixels per inch will result in fewer, larger half tone dots, and more pixels per inch will result in more, smaller halftone dots.
Save and print your halftone image on a sheet of heavyweight paper. Cut out the negative space in your image, which will include each halftone dot, with a utility knife to create your stencil.
Alternatively, if you don't have a graphics editing program, upload your image to a free online halftone pattern creator such as The Rasterbator. After uploading, crop and size your image and select the number of dots per inch. Download the finished image, and print it out on heavy weight paper to create your stencil.