A paper shredder is a paper-cutting machine, which has a number of built in sharp and very effective paper cutters, which shred a bulk of the waste papers, within minutes. Paper shredding requirements vary from person to person and user to user, e.g., the paper shredding requirements of a common citizen, who wants to save his skin from the watch dogs of the government departments, i.e. taxation or customs department etc, will vary from those of a business office, a government or non government organisation, a secret agency, or a factory, which operates at a huge level and is involved in paper shredding services for commercial purposes. Shredders employ various methods to shred a document, paper, a cheese cake, vegetable, a hard disk or the parts of an automobile vehicle. Basically, we need always to remember that the shredders are equipped with sharp, durable and strong cutting and the shredding blades, which shred the required stuff, quite effectively, within no time. These cutting and the shredding blades are fixed at the varying angles and these perform the multiple operations on the required stuff. A user may be at certain times interested in knowing about the mechanics of a paper shredder. Moreover, the shredding requirements and the needs of the users may be different with various users, depending upon their official commitments and the security concerns. For example, the shredding requirements of the people from a small business enterprise may be entirely different from the requirements faced by the employees of a secret service agency. Similarly, the shredding requirements of a common citizen may be entirely different from the shredding requirements of a commercial shredding or a paper recycling commercial unit.

Keeping in view the shredding needs of different people, shredders of various designs, employ varying techniques; i.e. the strip-cut shredders use rotating knives to cut narrow strips as long as the original sheet of paper. These strips can be reassembled by a determined investigator, so this type of shredder is the least secure. It also creates the highest volume of waste. The cross-cut or confetti-cut shredders use two contra-rotating drums to cut rectangular, parallelogram, or diamond-shaped shreds. We have the particle-cut shredders create tiny square or circular pieces. Another type of these shredders, i.e. the disintegrators and granulators repeatedly cut the paper at random until the particles are small enough to pass through a mesh. There are the hammermills, which pound the paper through a screen. The pierce and tear rotating bladecshredders, whose pierce and tear rotating blades pierce the paper and then tear it apart. Another important type is the grinder, which are equipped with a rotating shaft with cutting blades, which grind the paper until it is small enough to fall through a screen.

The papers shredders can be further classified into the various categories on the basis of the shredding methods employed by these. Due to the shredding methods employed by these, these shredders are classified into various types and various security levels, e.g. the paper shredders of level 1 cut the paper into 12 mm strips, The paper shredders of level 2 cut the paper into 6 mm strips. The paper shredders of level 3 cut the paper into 2 mm strips and are normally used to shred the confidential documents and the papers. On the other hand, the paper shredders of level 4 cut the paper into 2 x 15 mm particles and are used to shred the commercially sensitive papers and documents, the paper shredders of level 5 cut the paper into 0.8 x 12 mm particles. These are used to shred topsecret or classified papers and documents. The paper shredders of level 6 cut the paper into 0.8 x 4 mm particles and these again are used to shred the topsecret or classified documents.

There are a few other alternative shredders also, which destroy the documents by means of burning, chemical decomposition or composting for disposing etc.