Snoots are another form of light modifying equipment. They are open ended cylinders that are usually made of metal and then painted black. Snoots are placed at the front of a spotlight to limit the size of the circular area that is projected by the light. Wide, short snoots will provide a large circle of light. Long and narrow snoots will provide you with a narrow circle of light.
If you are in a situation that calls for a snoot and you don't have one you can improvise by using a cardboard tube or black, rolled piece of paper. Snoots are available in various sizes and can come in kits, be bought individually or in sets. They can be bought from as low as about $5 each.