Well I might just work up an article from this as well. Here is the start and first installment of several clasifications and writeups on various types of portals.
Common One Way Portal
The common portal is a naturally occuring phenomena linking two planes for relatively short durations of time when they are made active by some key or trigger. The common portal always opens from a bounded space but may exit anywhere-often but not nessasarily a similar bounded space in shape and dimension. Upon activation these portals allow transit from the side of activation to the side of termination by passing through the bounded space of the portal. Once through however these portals do not allow transit from the termination side to the activation side even if they are re-activated or kept active from the activation side. When objects of larger volumes pass through these portals than their termenation sides will accomodate the most likely result is simply a blockage and eventual cut off and physical seperation of the object when the portal deactivates. However other interesting results have been reported and recorded especially with living creatures. Some portals will not close while a living creature is passing through them. Others have been reported to close on the creatures yet leaving the seperated parts of the creature intact and somehow connected. Othertimes forces will shunt the creature or object one way or the other through the portal. Individual portals will tend to act in different ways from one another or from one activation to the next though most will act consistently in one particular way with each activation. Of the class of these portals that consistently severs objects caught between the sides at deactivation there have been several interesting tests done to see just how strong the severing forces are. If anything my last research group has found that yes an indestructable Staff of the Great Mage can be severed, and if severed its ensuing destruction is quite spectacular. The funds are still being gathered for two of that party's resurections. These results may however lead to applications for severing hard to sever items; though we must recomend testing the portal on non-volitile smaller items first and useing mechanical holding devices in order to keep a safe distance in cases of severing items of signifigant magical power, taking cover is also highly recomended in such cases as well.