Knife

Stanley Knife

Stanley knife

Also known as a utility knife
Retractable and fixed blade versions
Stanley is a brand name often used for this type of knife, regardless of brand.
The toughest of the knives popular for DIY

Wallpaper knife

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Wallpaper knives

Lightweight disposable plastic knife with snap-off segmented blade
9mm & 18m blades
Very cheap, many for £1
Widely used for tasks where high strength is not needed
Blades easy to replace
Durable metal bodied versions also exist.

Pocket Knife

Pocket knife

The forerunner of the above knife types, these are no longer popular for DIY use, but are still used by some.

Higher initial purchase price, zero ongoing costs
The non-replaceable blade(s) must be resharpened
Most types can snap shut on fingers in some situations, which is not really a Good Thing.
Heavier and bulkier than wallpaper knives
Some pocket knives include other small tools, which usually prove to be more useful for inflicting minor self injury than DIY.

Craft knife, X-acto knife

Xacto craft knife

These are small knives sometimes used in DIY, but more popular for craft use. The handles are somewhat like a writing pen, and the blades used are scalpel blades and other blades of a similar size.

Many blade shapes are available.
X-Acto is another trade mark that has fallen into general usage

Scalpel

Scalpels

More used for DIY surgery than house maintenance, the most popular pattern of these is a 1 piece metal handle with no moving parts, into which the scalpel blade snaps into place. Designed for sterilisability.

Disposable plastic handles scalpels are also common
Useful for removing splinters, and other very fine work

Carving Knife

Kitchen knives are not much used for DIY, but mean looking serrated ones can be used as an effective chipboard saw if caught without the right tools.

Electrician's knife

Insulated handle
Used to cut wire insulation

Lead knife

for lead roofing
Long hook-nosed blade

Carbide tipped knife

Tough long lasting carbide tip
Massively outlasts steel blades
Good for use on tough workpieces, such as tile backing board
Hardibacker carbide tipped knife

Blades

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2x wallpaper knife blades 9mm & 18mm. Stanley type

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Popular scalpel blade shapes

Blades in bulk