  We present data from long ROSAT HRI observations of the intermediate polars
YY Dra and V709 Cas which show that V709 Cas, like YY Dra, exhibits a
double-peaked X-ray pulse profile. Neither system shows evidence for X-ray beat
period or orbital modulation, so both must be disc-fed accretors seen at low
inclination angles. We argue that the short spin periods of the white dwarfs in
these objects indicate that they have weak magnetic fields, so the radius at
which material is captured by the field lines is relatively small. Consequently
the footprints of the disc-fed accretion curtains on the white dwarf surface
are large. The optical depths to X-ray emission within the accretion curtains
are therefore lowest in the direction along the magnetic field lines, and
highest in the direction parallel to the white dwarf surface, such that the
emission from the two poles conspires to produce double-peaked X-ray pulse
profiles. We emphasise that such a pulse profile is not a unique indicator of
two-pole accretion however. Indeed, two-pole accretion onto smaller regions of
the white dwarf surface may be considered the `normal' mode of behaviour in a
disc-fed intermediate polar with a longer white dwarf spin period (and
therefore a higher field strength), resulting in a single-peaked pulse profile.
Collating data on other intermediate polars, we may classify them into two
subsets. Fast rotators, with relatively weak fields, show double-peaked pulse
profiles (AE Aqr, DQ Her, XY Ari, GK Per, V709 Cas, YY Dra, V405 Aur), whilst
slower rotators, with larger fields and therefore larger magnetospheres, have
been seen to exhibit an X-ray beat period modulation at some time (FO Aqr, TX
Col, BG CMi, AO Psc, V1223 Sgr, RX J1712.6-2414).
