#include <bits/stdc++.h>
using namespace std;
void solve() {
  long long int a, b, c, d, m, n, p, q, r, x, y, z, aa, bb, cc, dd;
  long long int i, j, k, l;
  long long int cnt = 0, cnt1 = 0, cnt2 = 0, cnt3 = 0, sum = 0, mx = LLONG_MIN,
                mn = LLONG_MAX;
  long long int flag = 0, flag2 = 0;
  vector<long long int> vec1, vec2, vec3;
  string s1, s2, s3;
  cin >> n;
  pair<long long int, long long int> pr;
  set<pair<long long int, long long int>> st;
  set<pair<long long int, long long int>>::iterator it;
  for (long long int i = (long long int)(0); i < (long long int)(n); ++i) {
    cin >> a >> b;
    pr = make_pair(a, b);
    st.insert(pr);
  }
  it = st.begin();
  x = it->second;
  it++;
  for (it = it; it != st.end(); it++) {
    if (it->second < x) {
      flag = 1;
      break;
    }
    x = it->second;
  }
  if (flag)
    cout << "NO\n";
  else {
    x = 0;
    y = 0;
    cout << "YES\n";
    for (it = st.begin(); it != st.end(); it++) {
      p = it->first - x;
      for (long long int j = (long long int)(0); j < (long long int)(p); ++j)
        cout << "R";
      q = it->second - y;
      for (long long int j = (long long int)(0); j < (long long int)(q); ++j)
        cout << "U";
      x = it->first;
      y = it->second;
    }
    cout << endl;
  }
}
int main() {
  ios::sync_with_stdio(false);
  long long int t = 1;
  cin >> t;
  while (t--) {
    solve();
  }
  return 0;
}
