Which technique involves the use of a straight razor?

The technique that involves the use of a straight razor is shaving. Shaving traditionally employs a straight razor for achieving a close and smooth shave, particularly on the face and neck. This tool allows for precise control and can create sharp lines along the beard or hairline, making it a favored choice in classic barbering.

In contrast, the other techniques serve different purposes within hairstyling. Texturizing generally refers to techniques that modify the hair's texture, creating movement and reducing bulk without removing length. Layering focuses on cutting hair at varying lengths to create depth and volume, which can enhance the overall shape of a hairstyle. Blending is a technique used to seamlessly transition two different lengths or textures within a haircut to achieve a uniform look. Each of these methods does not involve the use of a straight razor as a primary tool.