Lego's official position on this technique was explained at
Brickfest 2006. Jamie Berard, then a relatively new designer in
Billund gave an excellent presentation on why certain techniques
are considered "illegal" in official sets. The basics message is
that building techniques should: - not stress the bricks - be
suitable for the target audience of the set He described in some
detail the ways that Technic beams and regular system bricks can
and cannot be combined in official sets. The main problem areas
occur because: - Technic holes don't exactly line up with the
studs on the sides of system bricks - the holes in Technic beams
are slightly smaller than the ones in system bricks The
implications are: - Although system brick studs can be inserted
in the holes in technic beams, this should be avoided where it
would be difficult for children to take apart. Jamie gives an
example where a brick has a single stud inserted into a beam,
and describes it as "tehnically legal" (but not recommended).
This is the situat