The design and construction of the pipe-bomb in the past three years in Northern Ireland has shown almost no bomb-making skill among anti-agreement loyalists.
In the same period anti-agreement republicans, by contrast, have evolved high-standard improvised landmines, under-car bombs and mortars.
The loyalist pipe-bomb is a length of steel pipe sealed with solder at one end. "Fragmentation lines" - usually diamond-shaped cuts like those on cut glass - are machined into the surface of the pipe to replicate the shrapnel fragmentation of proper grenades.
The filling is "black powder" taken from ordinary fireworks. Sometimes ball-bearings are inserted to increase the shrapnel effect.
A short length of fuse is then inserted into an explosive cap at the open end. The fuse is lit and the device thrown through a window, left on a window sill or pushed through a letter box.
One person has been killed. Mrs Elizabeth O'Neill (59), a mother of two, died on June 5th, 1999 when she lifted a pipebomb thrown through her window in the predominantly loyalist Corcrain Drive estate in Portadown. She was a target because she was married to a Catholic.
In most cases the devices fail to explode. However, dissident loyalists in Co Down have improved the effectiveness of their devices slightly. A pipe-bomb with a trip-wire caused serious leg injuries to an RUC officer there on November 2nd last.
The latest spate of attacks arises from a decision by sections of the UDA to end their ceasefire and begin a low-level campaign of terror against Catholics living in predominantly Protestant areas.
This decision to move back towards a war footing, as it were, is understood to be a reaction to the increased frequency of dissident republican attacks.
Before the ending of the UDA ceasefire, there were about 30 pipe-bomb attacks in counties Tyrone, Armagh, Derry, Antrim and Down. This purely sectarian campaign began in April 1998 in the aftermath of the signing of the Belfast Agree ment.
These attacks were claimed in the names of the Orange Volunteers, a UDA-affiliated group in Co Down, and the Red Hand Defenders, a similar group based in Co Antrim.
Information about crude bombs is available on the Internet. The RUC has found that some loyalist bombs of the past two years are similar to designs on the Internet.
The sites include reasonably accurate information about the damage that can be caused by shrapnel, explosive components, timers and detonators.
These devices, referred to sometimes by police as `Internet bombs', were constructed by students Eric Harris (18) and Dylan Klebold (17) of Denver, Colorado, who carried out the massacre at Columbine High School.
As well as opening fire on pupils and staff with a variety of weapons, they planted about 30 pipe-bombs during their rampage on April 20th, 1999.