The scaffold (or scaffolding) is a very useful, multiporpuse, "heavy duty" pattern, it can be used as a rock, and eater, and others. The fact that it is almost indestructible makes it very useful for "machines".
x = 5, y = 5, rule = extendedlife 2A.2A$.3F$AF.FA$.3F$2A.2A!
It is also able to eat spaceships, blocks, and even stabilise the queen bee shuttle, as shown below:
x = 81, y = 10, rule = extendedlife 47.A.A$33.A14.A$66.A$3.2A.2A.2A8.2A.2A7.2A.2A10.2A.2A4.2A.2A4.A.A9.2A .2A$2A2.3F2.2A9.3F9.3F12.3F6.3F4.A.A11.3F$2A.A3FA11.A3FA7.A3FA10.A3FA 4.A3FA2.A2.A9.A.3FA$4.3F13.3F9.3F12.3F6.3F4.A.A11.3F$3.2A.2A11.2A.2A 7.2A.2A10.2A.2A4.2A.2A4.A.A9.2A.2A$21.A44.A$33.A!