<s>
An	O
overlay	B-Device
keyboard	I-Device
or	O
concept	B-Device
keyboard	I-Device
is	O
a	O
specialized	O
keyboard	B-Device
with	O
no	O
preset	O
keys	O
.	O
</s>
<s>
Overlay	B-Device
keyboards	I-Device
are	O
often	O
used	O
as	O
a	O
quick	O
and	O
easy	O
way	O
to	O
input	O
items	O
with	O
just	O
two	O
buttons	O
.	O
</s>
<s>
Overlay	B-Device
keyboards	I-Device
generally	O
consist	O
of	O
a	O
flat	O
grid	O
of	O
unmarked	O
buttons	O
.	O
</s>
<s>
A	O
sheet	O
called	O
an	O
overlay	O
is	O
placed	O
on	O
the	O
keyboard	B-Device
to	O
identify	O
each	O
key	O
,	O
after	O
the	O
keyboard	B-Device
is	O
programmed	O
.	O
</s>
<s>
Overlay	B-Device
keyboards	I-Device
have	O
several	O
advantages	O
over	O
conventional	B-Device
keyboards	I-Device
or	O
mice	B-Device
.	O
</s>
<s>
nor	O
do	O
they	O
require	O
a	O
great	O
deal	O
of	O
fine	O
motor	O
control	O
,	O
making	O
them	O
ideal	O
for	O
people	O
who	O
have	O
difficulty	O
using	O
a	O
conventional	O
keyboard	B-Device
.	O
</s>
<s>
Overlay	B-Device
keyboards	I-Device
are	O
easy	O
to	O
clean	O
,	O
and	O
resistant	O
to	O
spills	O
or	O
dust	O
.	O
</s>
<s>
The	O
ability	O
to	O
change	O
overlay	O
sheets	O
also	O
makes	O
it	O
easy	O
for	O
a	O
single	O
overlay	B-Device
keyboard	I-Device
to	O
have	O
several	O
different	O
uses	O
.	O
</s>
<s>
Overlay	B-Device
keyboards	I-Device
are	O
probably	O
most	O
often	O
found	O
in	O
fast	B-Application
food	I-Application
restaurants	O
,	O
where	O
they	O
reduce	O
the	O
amount	O
of	O
time	O
required	O
to	O
enter	O
items	O
.	O
</s>
<s>
Overlay	B-Device
keyboards	I-Device
are	O
also	O
used	O
in	O
education	O
,	O
especially	O
at	O
the	O
primary	O
level	O
.	O
</s>
