New techniques for obtaining lower bounds on string-matching problems are developed and we prove the following new results. String-matching cannot be performed by a three-head one-way deterministic finite automaton. This answers the $k=3$ case of the open question, due to Galil and Seiferas [GS], whether a $k$-head one-way deterministic finite automaton can perform string-matching. String-matching by a k-head two-way DFA with k-1 heads blind (can only see two end symbols) is studied, tight upper and lower bounds are provided. Probabilistically moving a string on one tape (requiring $n^{2}$ time) is harder than probabilistically matching two strings on 1 tape. Notice that this is not true for deterministic or even nondeterministic TMs. This is the first result showing that checking is easier than generating.