In some BDSM sessions, the top exposes the bottom to a range of sensual experiences, such as pinching; biting; scratching with fingernails; erotic spanking; erotic electrostimulation; and the use of crops, whips, liquid wax, ice cubes, and Wartenberg wheels. Fixation by handcuffs, ropes, or chains may occur. The repertoire of possible "toys" is limited only by the imagination of both partners. To some extent, everyday items, such as clothespins, wooden spoons, and plastic wrap, are used in sex play. It is commonly considered that a pleasurable BDSM experience during a session dependends strongly on the top's competence and experience and the bottom's physical and mental state. Trust and sexual arousal help the partners enter a shared mindset.