Question: How do snoRNAs guide enzymes to spots along an RNA strand?
About the article "RNA", section "In RNA processing".

Candidate passages:
Small nucleolar RNA sR8 is a non-coding RNA belonging to the C/D box class of snoRNAs.
sR8, along with other C/D box snoRNAs, performs 2′-"O"-methylation of ribose on a target strand of ribosomal RNA.
Targeting is achieved through the C and D box components, which are short sections of conserved sequences, as well as C'/D' boxes (internal equivalents of the C and D boxes).
These sequences base-pair with nucleotides in the target rRNA to direct their methylation.
sR8 RNA operates alongside protein components in a ribonucleoprotein (RNP) complex.
sR8 is able to guide the methylation of targets found within structured stem-loops, which implies that a component of the complex is able to unwind such structures. 
Many RNAs are involved in modifying other RNAs.
Introns are spliced out of pre-mRNA by spliceosomes, which contain several small nuclear RNAs (snRNA), or the introns can be ribozymes that are spliced by themselves.RNA can also be altered by having its nucleotides modified to other nucleotides than A, C, G and U.
In eukaryotes, modifications of RNA nucleotides are in general directed by small nucleolar RNAs (snoRNA; 60-300 nt), found in the nucleolus and cajal bodies.
snoRNAs associate with enzymes and guide them to a spot on an RNA by basepairing to that RNA.
These enzymes then perform the nucleotide modification.
rRNAs and tRNAs are extensively modified, but snRNAs and mRNAs can also be the target of base modification.
RNA can also be methylated.
RNA replication is the copying of one RNA to another.
Many viruses replicate this way.
The enzymes that copy RNA to new RNA, called RNA-dependent RNA polymerases, are also found in many eukaryotes where they are involved in RNA silencing.
RNA editing, in which an RNA sequence is altered by a complex of proteins and a "guide RNA", could also be considered an RNA-to-RNA transfer. 
Small nucleolar RNAs (snoRNAs) are a class of small RNA molecules that primarily guide chemical modifications of other RNAs, mainly ribosomal RNAs, transfer RNAs and small nuclear RNAs.
There are two main classes of snoRNA, the C/D box snoRNAs, which are associated with methylation, and the H/ACA box snoRNAs, which are associated with pseudouridylation.
SnoRNAs are commonly referred to as guide RNAs but should not be confused with the guide RNAs that direct RNA editing in trypanosomes. 
In molecular biology, the small nucleolar RNAs SNORD106 and SNORD12 (also known as U106 and HBII-99 respectively ) are two related snoRNAs which belongs to the C/D class of small nucleolar RNAs (snoRNAs).
Both contain the conserved C (UGAUGA) and D (CUGA) box sequence motifs Human SNORD12 (HBII-99) is the homologue of mouse snoRNA MBII-99.
In humans both HB11-99 and U106 snoRNAs share the same host gene.
Most of the members of the box C/D family function in directing site-specific 2'-O-methylation of substrate RNAs.
HBII-99 is predicted to guide the 2'O-ribose methylation of 28S rRNA G3878.
U106 contains conserved antisense elements which would predict U106 methylates residues G1536 and U1602 of 18S rRNA.
However, these targets do not appear to be methylated and U106 might function as an RNA chaperone during rRNA folding.
A similar role has been suggested for the H/ACA snoRNAs U17a and U17b