It sounds like the pieces of scaffolding fit together by having built-in pins and sockets like a Lego set, rather than needing to be bolted together. Can you give us more context?

I think one needs to know at least the medium and size of this piece to know how it should be translated. Does the "por encastre" refer to supports used during its construction (for example, in a cast metal sculpture) or an assembly method by which all the pieces of a finished work are screwed or clamped together to keep it rigid and intact or even to make it free-standing? If the latter is the case, the sentence will need to be completely restructured. Without a picture or more information, it is impossible to know. encastre [constr.] - eingespannt
Contexto/ Ejemplos
http://unabridged.merriam-webster.com/unabridged/encastre
en·cas·tre
adjective
: built in at the supports
Origin of ENCASTRE

French encastré, past participle of encastrer to embed, fit into a recess, from Italian incastrare, from Late Latin, from Latin in + castrare to trim, cut off, castrate
http://dict.tu-chemnitz.de/english-german/encastre.html
Englisch Deutsch
built-in; encastre; encastré eingespannt {adj}http://dict.leo.org/forum/viewWrongentry.php?idThread=122081... Built-in or Fixed or Encastre Support:

It is a support which restrains complete movement of the beam both in position as well as direction. The support gives all of the three relevant reactions (say Rx, Ry and Mz), that means the reactions in x and y directions and fixing moment Mz. In other terms, the fixed support offers resistance against translation in both the directions and also against the rotation.http://www.expertsmind.com/topic/types-of-support/fixed-or-e...‎
11/4/2012 - Dead loads are loads that act on a structure all the time and include its self-weight, .... 1.13(b) and is called a fixed, built-in or encastré support.http://www.slideshare.net/huyxp/structural-and-stress-analys...

A suggestion, depending on the type of fitting. See web page below.