What is a Taping Knife?

A taping knife, also known as a drywall knife or a joint knife, is a construction instrument principally used for applying and smoothing drywall joint compounds. It is a flat, rectangular-shaped blade that spans lengths from 4 to 14 inches and features a flexible, thin, and lightweight stainless steel blade. Taping knives are utilized to apply a thin coating of joint compound to plasterboard seams and joints before feathering and smoothing the compound’s edges to produce a seamless surface. In addition, they are utilized for scraping, spreading, and smoothing materials such as plaster, putty, and caulk. Taping knives are an indispensable tool for any expert or do-it-yourselfer who wants a smooth, professional finish on their plasterboard or other building projects.

Given the importance of taping knives, it is essential to select the proper one for you and your job. The variety of possibilities, however, might be overwhelming: size, handle material, blade material, and unique features. How are you to choose which knife is ideal for you? This comprehensive guide eliminates the guesswork involved in selecting the best knife for you and your job.



Size may be the single most significant factor to consider when selecting a tape knife, as it dictates the stage of construction for which the knife is most suited. Smaller knives, six inches and under, are frequently referred to as joint knives and are ideal for the first phases of a project. Their diminutive size permits access to tighter areas and crevices, as well as the use of greater power to shove mud into seams and screw holes. Moreover, joint knives have rounded, sloping sides. This allows the knife to fit into corners without causing damage to the wall. Smaller knives are more likely to leave markings and uneven surfaces, but in the beginning, this is OK because you will apply a second coat.

Bigger knives (six inches or longer) are ideal for finishing since they allow you to cover more land with less force. These knives are excellent for smoothing the tracks left by smaller knives, feathering muck, and overall leaving a clean surface in the last phases of a job when detailing is complete. These bigger blades are typically referred to as tape knives and have a square form.

The five- or six-inch knife merits special consideration, since this size fills a unique niche. As a result of its suitability for both mud application and detail/finishing work, it is the most popular size. Because of this, many experts opt to have multiple six-inch knives on available for any given project. Flexibility is the most crucial consideration when selecting a six-incher, which takes us to:


In general, stainless steel, carbon steel, and blue steel are utilised to construct the blades of tape knives. Carbon steel blades are unusual, however, they are infrequently encountered. The distinctions between the materials may not be immediately evident, so let’s examine them separately.

Stainless Steel

Stainless steel, a specific type of steel that is resistant to corrosion and includes up to 10.5% chromium, is one of the two most used materials for knife blades. The key reason is its durability: stainless steel is extremely durable and robust. A stainless steel knife will survive for many years if maintained properly. Yet, stainless steel is less flexible than other knife materials due to its durability-enhancing hardness. As a result, it will have a more difficult time feathering muck, entering corners, and bending permanently than other blade kinds. However, stainless steel is more difficult to sand to a fresh edge than softer steel alloys.

Carbon Steel

Carbon steel is substantially more flexible than stainless steel, making it ideal for feathering, smoothing, and other delicate operations. Nonetheless, carbon steel is highly susceptible to corrosion. As a result, it is more difficult to maintain and is not a popular material for blades.

Blue Steel

Blue steel is carbon steel that has been treated to prevent corrosion. This treatment produces a dark, blue-black surface, from which this alloy derives its name. Blue steel is more malleable than stainless steel and more resistant to corrosion than carbon steel. In general, blue steel is chosen by more seasoned plasterboard specialists because to its pliability, which is the the finest utilised by people with a steady hand and extensive knowledge making extremely subtle changes. It still requires more care than stainless steel, but may be readily maintained by adding a little layer of oil between usage.


Common handle materials include wood, plastic, and rubber. Several considerations, such as affordability, durability, and comfort, will determine which option you select.


Wooden handles are conventional and favored by individuals who value comfort and durability. They are aesthetically pleasing, withstand the demands of the job well, and are pleasant to grip. Nevertheless, wood handles are more costly and heavier than other choices, so while they are attractive, they can make carrying a large number of knives burdensome. Some manufacturers provide wood handles on their brand of knives, while others offer them as an option on other lines.


It is affordable and long-lasting, making it a budget-friendly option. It will last for a long period with minimal up-front cost. Hard plastic grips are often considered less pleasant than alternative solutions (with some exceptions).


It is a versatile material that combines durability and comfort. Rubber’s enhanced traction enables the user to apply or manipulate mud with a lighter touch. Hence, rubber-handled knives are ideally suited for precise jobs involving feathers and finishing touches.


In addition to the handle material, there are a number of design factors that might impact the use or comfort of a specific tape knife.

Offset Handle

These knives eschew the “handle in line with blade” form in favour of a shape that displaces the handle from the blade. This increases finger clearance and decreases the likelihood of accidently marking the mud with your knuckles. This also allows the knife to be brought closer to the wall, making it simpler to create a flawless finish.

Long Handles

Some knives have an extended handle that makes it easier to reach the ceiling or other difficult-to-reach regions. They sacrifice additional reach for higher weight and less portability on the job site.

Finished Handles

Some knives have plastic handles covered with another substance, typically rubber or another material having a pleasant touch. These knives aim to combine the comfort and light feel of rubber handles with the affordability and durability of plastic handles.


Some plasterboard contractors utilise blades, while others use trowels. Behind a trowel’s offset handle is a blade with a bigger surface area (leading in faster smoothing times) (no way to leave finger marks or indentations). On the other hand, they require more experience (particularly for feathering) and are less suitable to tiny areas, so you may find that a combination of trowels and knives is optimal.

The greatest professional-grade trowels are often only available in stainless steel, as they do not require flexibility like blades. Nonetheless, you may still find the same handle alternatives as on taping knives (wood, plastic, rubber).


Several manufactures differentiate between joint knives and taping knives. Joint knives are typically smaller (6″ and lower) than tape knives (6″ and above). As can be seen (and as stated previously), this makes the 6-inch knife the most adaptable size. In addition, joint knives resemble putty knives in appearance (rounded, sloping sides from the blade to the handle), but they are not sharpened like putty knives. In contrast, tape knives are often more rectangular. While they are interchangeable in some applications, the variation in form results from the necessity for a knife that can operate within corners; the smaller size and rounded shape make it simpler to work around corners without scraping or injuring the surface (though nowadays, many people use a specially-designed corner trowel for this job)

Bottom Line

Taping knife is an indispensable item that no drywall installer or repairman should be without. It enables the application of joint compounds easier and more efficient and contributes to the creation of a flawless finish. With so many different types and sizes of tape knives available on the market, it is essential to select one that is suitable for the task at hand and fulfills your requirements. Hence, whether you are a seasoned professional or a novice, purchasing a high-quality tape knife is a worthwhile investment.

I love knives and love reviewing them. Knives have been a part of our lives for as long as we can remember. We grew up using knives in the kitchen and in outdoors.