SUMMARY
The functional approach is one of the most general approaches in geometrical modeling. The functional approach describes complex geometrical objects (like engines, aircrafts, etc.) using mathematical formulas. A popular method for representation geometrical object in mathematical formulas uses implicit functions. These implicit functions can be constructed using logical operations under functions called R-functions represent logical operations (negation, conjunction, disjunction, etc) under implicit functions. A fastener is a hardware device that mechanically joins or affixes two or more objects together. In the article authors propose geometrical models based on R-functions for different fasteners (some types of bolts, nuts). In the first section of the article authors describe implicit functions for representation of basic primitives (a regular polygon, a chamfer). The next section aims to obtain of 3D models of fasteners using R-functions under primitives. Some visual examples are shown in the final section.