A sack which does not allow room for full extension of the limbs is very much more potent. Even a slight reduction of mobility, without any other restrictions, can very quickly have a telling effect on both mind and body. Limbs soon react painfully and the mind acknowledges not only the discomfort but the vulnerability much sooner. Adjusting to the limited (though perfectly adequate) supply of air demands quite strenuous mental exercise. If the internal size of the bag is gradually reduced, the situation can soon become intensely oppressive.
Not knowing what is going on outside or hearing sounds which may or may not be interpreted correctly is, in itself, powerfully effective.
The head outside a sack which is closed around the neck can perhaps intensify the feeling of vulnerability.
The neck cord need not be tight if wrists are secured inside the bag.
Suspension: If the sack is hung, putting body weight onto the 'walls' of the confined area, the physical experience is altered
completely, and can quickly become barely tolerable.
N.B. The strength and durability of any sack used for suspension mus t be equal to the task.
2. A BODYBAG
Similar in proportion to a conventional sleeping bag, this can also render the person inside totally helpless without any additional restraint being applied. Many games have evolved from normal camping expeditions. Aby tough Government Surplus oblong bag can be a very useful piece of equipment in it's natural state. Or, with modification can become more seriously restrictive. 'D' rings added to serve as anchor points (or to prevent external straps from being worked free) can make an ordinary bag very versatile.
Whether the head is inside or out, such a bag can keep somebody quite comfortable but totally confined for quite long periods. If the head is aside, a 'snorkel breathing pipe might be used to ensure an adequate supply of air (but constant monitoring is advisable). Bags made from waterproof or padded fabric can intensify the experience in terms of generated heat. Heavy clothes or additional restraints worn before the 'victim' is put into the bag can extend the parameters of the situation infinitely.
Being stood up or suspended within such a bag can completely change the tensions, but care must be taken. The possible danger of lifting or moving around the dead-weight of somebody who is totally helpless perhaps needs a separate 'worksheet'.
3. SLEEPSACK
This is a term I coined when designing the original configuration which has now become recognised world-wide. A form fitting type of full-length body-shaped bag with or without an attached head-cover. The main design feature is internal arm-sleeves which separate arms from the body and render the wearer helpless inside the bag.
Usually soft and malleable, a bag of this configuration can be made from canvas, leather or latex (if sufficiently strong).
Once inside, the body covering and attached 'D' rings can be used to subject a body to varying intensities of confinement through the use of added lacing or straps. Construction details depend entirely on the likes and dislikes of the users. As such 'Sleepsacks' are usually made to order, variations such access points, anchoring points, strap or lace tightening possibilities are all optional.